[RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

Disabling GS0 usage lets siw create FPDUs fitting MTU size.
Enabling GSO usage lets siw form larger FPDUs fitting up to one
current GSO frame. As a software only iWarp implementation, for
large messages, siw bandwidth performance severly suffers from not
using GSO, reducing available single stream bandwidth on fast links
by more than 50%, while increasing CPU load.

Experimental GSO usage handshake is implemented by using one spare
bit of the MPA header, which is used to signal GSO framing at
initiator side and GSO framing acceptance at responder side.
Typical iWarp hardware implementations will not set or interpret
that header bit. Against such peer, siw will adhere to forming
FPDUs fitting with MTU size. This assures interoperability with
peer iWarp implementations unable to process FPDUs larger than
MTU size.

Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
---
 drivers/infiniband/sw/siw/siw_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/sw/siw/siw_main.c b/drivers/infiniband/sw/siw/siw_main.c
index 5cd40fb9e20c..a2dbdbcacf72 100644
--- a/drivers/infiniband/sw/siw/siw_main.c
+++ b/drivers/infiniband/sw/siw/siw_main.c
@@ -36,7 +36,7 @@ const bool zcopy_tx = true;
  * large packets. try_gso = true lets siw try to use local GSO,
  * if peer agrees.  Not using GSO severly limits siw maximum tx bandwidth.
  */
-const bool try_gso;
+const bool try_gso = true;
 
 /* Attach siw also with loopback devices */
 const bool loopback_enabled = true;
-- 
2.20.1

RE: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----

>To: "Bernard Metzler" <bmt@zurich.ibm.com>, <faisal.latif@intel.com>,
><shiraz.saleem@intel.com>, <mkalderon@marvell.com>,
><aelior@marvell.com>
>From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>Date: 04/15/2020 12:52PM
>Cc: dledford@redhat.com, jgg@ziepe.ca, linux-rdma@vger.kernel.org,
><bharat@chelsio.com>, <nirranjan@chelsio.com>
>Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
>negotiation of GSO usage.
>
>On Tuesday, April 04/14/20, 2020 at 16:48:22 +0200, Bernard Metzler
>wrote:
>> Disabling GS0 usage lets siw create FPDUs fitting MTU size.
>> Enabling GSO usage lets siw form larger FPDUs fitting up to one
>> current GSO frame. As a software only iWarp implementation, for
>> large messages, siw bandwidth performance severly suffers from not
>> using GSO, reducing available single stream bandwidth on fast links
>> by more than 50%, while increasing CPU load.
>> 
>> Experimental GSO usage handshake is implemented by using one spare
>> bit of the MPA header, which is used to signal GSO framing at
>> initiator side and GSO framing acceptance at responder side.
>> Typical iWarp hardware implementations will not set or interpret
>> that header bit. Against such peer, siw will adhere to forming
>> FPDUs fitting with MTU size. This assures interoperability with
>> peer iWarp implementations unable to process FPDUs larger than
>> MTU size.
>> 
>> Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
>> ---
>>  drivers/infiniband/sw/siw/siw_main.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/infiniband/sw/siw/siw_main.c
>b/drivers/infiniband/sw/siw/siw_main.c
>> index 5cd40fb9e20c..a2dbdbcacf72 100644
>> --- a/drivers/infiniband/sw/siw/siw_main.c
>> +++ b/drivers/infiniband/sw/siw/siw_main.c
>> @@ -36,7 +36,7 @@ const bool zcopy_tx = true;
>>   * large packets. try_gso = true lets siw try to use local GSO,
>>   * if peer agrees.  Not using GSO severly limits siw maximum tx
>bandwidth.
>>   */
>> -const bool try_gso;
>> +const bool try_gso = true;
>>  
>>  /* Attach siw also with loopback devices */
>>  const bool loopback_enabled = true;
>> -- 
>> 2.20.1
>> 
>
>Hi Bernard,
>
>As per RFC5044, DDP layer should limit each record size to 
>MULPDU(Maximum ULPDU: The current maximum size of the record that
>is acceptable for DDP to pass to MPA for transmission)" 
>Eg: if physical layer MTU is 1500, then DDP record length should
>be ~1448 Max. All hard iWARP devices defaults to this behaviour, I
>think.
>		   
>So if SoftiWARP constructs FPDU based on this 64KB MSS, then the 

Hi Krishna,

The proposed patch does not nail it to 64K, but dynamically
adapts to what the TCP socket currently advertises.
This may vary over time, at maximum to 64K, or stick to 1.5K,
if advertised so. siw is not an ULP of Ethernet, but TCP, and
takes into account what the current TCP socket says.
TCP advertises to ULPs current maximum segments via
tcp_sock *tp->gso_segs for good reasons.

siw performance sucks when using small FPDUs, since it always
must attach a trailing CRC after any data pages it pushes. Adding
a 4 byte trailer after each data page to be sent seem to put the
kernel network stack far out of its comfort zone.

>hardiWARP peer(say Chesio adapter) should also understand the 64KB
>FPDU.

This is why it is currently disabled.

>At present, Chelsio T6 adapter could understand upto 16KB large FPDU
>size, max.
>
That's interesting and would already better the performance for
siw <-> hardware iwarp substantially I guess. Did you try that?

The siw code already has a hook to limit segment growing below
to what TCP advertises (since I experimented with earlier Chelsio
hardware which was able to accept different max segment sizes,
some up to full GSO (64k)). See siw.h:
u8 gso_seg_limit; /* Maximum segments for GSO, 0 = unbound */

While currently set to 1 during connection establishment for
not using GSO, other values would be respected. A '2' 
with 9k MTU would produce 16K FPDUs max.
 

>So is there a way that the peer(typically hard iWARP) could negotiate
>it's supported ingress FPDU size? instead of fixed 64KB size.
>
Again, it would not be fixed to 64K, but to what TCP tells siw.

In any case, thinking about that would make sense only if there
is interest from hardware side. Is there interest? Probably yes,
since single stream siw <-> siw on a 100Gb link with GSO would
have more than twice the throughput of siw <-> T6 w/o GSO ;)

>Adding other iWARP maintainers for wider audience, to let them share
>their thoughts. And if their adapters also have such ingress FPDU
>size
>limitations then I think allowing peer to negotiate its supported
>ingress
>FPDU size would be more efficient than going with fixed 64KB FPDU
>size.

I agree, would be great to get input from Intel and Marvell
as well...

Thanks for reviewing!
Bernard.

Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard Metzler wrote:
> >At present, Chelsio T6 adapter could understand upto 16KB large FPDU
> >size, max.
> >
> That's interesting and would already better the performance for
> siw <-> hardware iwarp substantially I guess. Did you try that?
Yes I see almost 3x perfromace gain when GSO is enabled.
That is, on a siw<->T6 setup, with 1500 MTU size:
GSO disabled: ~25Gbps
GSO enabled:  ~72Gbps

Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

[-- Attachment #1: Type: text/plain, Size: 478 bytes --]

On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard Metzler wrote:
Hi Bernard,

The attached patches enables the GSO negotiation code in SIW with
few modifications, and also allows hardware iwarp drivers to advertise
their max length(in 16/32/64KB granularity) that they can accept.
The logic is almost similar to how TCP SYN MSS announcements works while
3-way handshake.

Please see if this approach works better for softiwarp <=> hardiwarp
case.

Thanks,
Krishna. 

[-- Attachment #2: siw.patch --]
[-- Type: text/plain, Size: 7925 bytes --]

diff --git a/drivers/infiniband/sw/siw/iwarp.h b/drivers/infiniband/sw/siw/iwarp.h
index e8a04d9c89cb..fa7d93be5d18 100644
--- a/drivers/infiniband/sw/siw/iwarp.h
+++ b/drivers/infiniband/sw/siw/iwarp.h
@@ -18,12 +18,34 @@
 #define MPA_KEY_REQ "MPA ID Req Frame"
 #define MPA_KEY_REP "MPA ID Rep Frame"
 #define MPA_IRD_ORD_MASK 0x3fff
+#define MPA_FPDU_LEN_MASK 0x000c
 
 struct mpa_rr_params {
 	__be16 bits;
 	__be16 pd_len;
 };
 
+/*
+ * MPA reserved bits[4:5] are used to advertise the maximum FPDU length that an
+ * endpoint is willing to accept, like TCP SYN MSS announcement. This is an
+ * experimental enhancement to RDMA connection establishment. Both local and
+ * remote endpoints must use these flags, if at least, one endpoint wants to
+ * advertise it's capability to receive large FPDU length.
+ * As SIW driver sits on top of TCP/IP stack it can use GSO for sending large
+ * FPDUs(upto 64K - 1, capped due to 16bit MPA len), thus improves performance.
+ * Making use of bits[4:5] backwards compatibility with the original MPA Frame
+ * format, IE, rules defined in RFC5044, regarding FDPU length, should be
+ * followed when these bits are zero.
+ * TODO make this experimental feature tunable via module params, as the remote
+ * endpoint might also be using these reserve bits for other experiments.
+ */
+enum {
+	MPA_FPDU_LEN_DEFAULT = cpu_to_be16(0x0000),
+	MPA_FPDU_LEN_16K = cpu_to_be16(0x0400),
+	MPA_FPDU_LEN_32K = cpu_to_be16(0x0800),
+	MPA_FPDU_LEN_64K = cpu_to_be16(0x0c00)
+};
+
 /*
  * MPA request/response header bits & fields
  */
@@ -32,7 +54,6 @@ enum {
 	MPA_RR_FLAG_CRC = cpu_to_be16(0x4000),
 	MPA_RR_FLAG_REJECT = cpu_to_be16(0x2000),
 	MPA_RR_FLAG_ENHANCED = cpu_to_be16(0x1000),
-	MPA_RR_FLAG_GSO_EXP = cpu_to_be16(0x0800),
 	MPA_RR_MASK_REVISION = cpu_to_be16(0x00ff)
 };
 
diff --git a/drivers/infiniband/sw/siw/siw.h b/drivers/infiniband/sw/siw/siw.h
index dba4535494ab..a8e08f675cf4 100644
--- a/drivers/infiniband/sw/siw/siw.h
+++ b/drivers/infiniband/sw/siw/siw.h
@@ -415,7 +415,7 @@ struct siw_iwarp_tx {
 	u8 orq_fence : 1; /* ORQ full or Send fenced */
 	u8 in_syscall : 1; /* TX out of user context */
 	u8 zcopy_tx : 1; /* Use TCP_SENDPAGE if possible */
-	u8 gso_seg_limit; /* Maximum segments for GSO, 0 = unbound */
+	u16 large_fpdulen; /* max outbound FPDU len, capped by 16bit MPA len */
 
 	u16 fpdu_len; /* len of FPDU to tx */
 	unsigned int tcp_seglen; /* remaining tcp seg space */
@@ -505,7 +505,6 @@ struct iwarp_msg_info {
 
 /* Global siw parameters. Currently set in siw_main.c */
 extern const bool zcopy_tx;
-extern const bool try_gso;
 extern const bool loopback_enabled;
 extern const bool mpa_crc_required;
 extern const bool mpa_crc_strict;
diff --git a/drivers/infiniband/sw/siw/siw_cm.c b/drivers/infiniband/sw/siw/siw_cm.c
index 8c1931a57f4a..abeed777006f 100644
--- a/drivers/infiniband/sw/siw/siw_cm.c
+++ b/drivers/infiniband/sw/siw/siw_cm.c
@@ -712,6 +712,38 @@ static int siw_proc_mpareq(struct siw_cep *cep)
 	return -EOPNOTSUPP;
 }
 
+/*
+ * Sets/limits max outbound FPDU length based on the length advertised
+ * by the peer.
+ */
+static void siw_set_outbound_fpdulen(struct siw_cep *cep,
+				     struct mpa_rr_params *params,
+				     u16 *outbound_fpdulen)
+{
+	switch (params->bits & MPA_FPDU_LEN_MASK) {
+	case MPA_FPDU_LEN_16K:
+		*outbound_fpdulen = SZ_16K - 1;
+		break;
+	case MPA_FPDU_LEN_32K:
+		*outbound_fpdulen = SZ_32K - 1;
+		break;
+	case MPA_FPDU_LEN_64K:
+		*outbound_fpdulen = SZ_64K - 1;
+		break;
+	default:
+		WARN(1,
+		  "Peer advertised invalid FPDU len:0x%x, proceeding w/o GSO\n",
+		  (params->bits & MPA_FPDU_LEN_MASK) & 0xffff);
+
+		/* fpdulen '0' here disables sending large FPDUs */
+		*outbound_fpdulen = 0;
+		return;
+	}
+	siw_dbg_cep(cep, "Max outbound FPDU length set to: %d\n",
+			*outbound_fpdulen);
+	return;
+}
+
 static int siw_proc_mpareply(struct siw_cep *cep)
 {
 	struct siw_qp_attrs qp_attrs;
@@ -750,10 +782,12 @@ static int siw_proc_mpareply(struct siw_cep *cep)
 
 		return -ECONNRESET;
 	}
-	if (try_gso && rep->params.bits & MPA_RR_FLAG_GSO_EXP) {
-		siw_dbg_cep(cep, "peer allows GSO on TX\n");
-		qp->tx_ctx.gso_seg_limit = 0;
-	}
+	if (rep->params.bits & MPA_FPDU_LEN_MASK)
+		siw_set_outbound_fpdulen(cep, &rep->params,
+					 &qp->tx_ctx.large_fpdulen);
+	else
+		qp->tx_ctx.large_fpdulen = 0;
+
 	if ((rep->params.bits & MPA_RR_FLAG_MARKERS) ||
 	    (mpa_crc_required && !(rep->params.bits & MPA_RR_FLAG_CRC)) ||
 	    (mpa_crc_strict && !mpa_crc_required &&
@@ -1469,8 +1503,7 @@ int siw_connect(struct iw_cm_id *id, struct iw_cm_conn_param *params)
 	}
 	__mpa_rr_set_revision(&cep->mpa.hdr.params.bits, version);
 
-	if (try_gso)
-		cep->mpa.hdr.params.bits |= MPA_RR_FLAG_GSO_EXP;
+	cep->mpa.hdr.params.bits |= MPA_FPDU_LEN_64K;
 
 	if (mpa_crc_required)
 		cep->mpa.hdr.params.bits |= MPA_RR_FLAG_CRC;
@@ -1602,10 +1635,12 @@ int siw_accept(struct iw_cm_id *id, struct iw_cm_conn_param *params)
 	}
 	siw_dbg_cep(cep, "[QP %d]\n", params->qpn);
 
-	if (try_gso && cep->mpa.hdr.params.bits & MPA_RR_FLAG_GSO_EXP) {
-		siw_dbg_cep(cep, "peer allows GSO on TX\n");
-		qp->tx_ctx.gso_seg_limit = 0;
-	}
+	if (cep->mpa.hdr.params.bits & MPA_FPDU_LEN_MASK)
+		siw_set_outbound_fpdulen(cep, &cep->mpa.hdr.params,
+					 &qp->tx_ctx.large_fpdulen);
+	else
+		qp->tx_ctx.large_fpdulen = 0;
+
 	if (params->ord > sdev->attrs.max_ord ||
 	    params->ird > sdev->attrs.max_ird) {
 		siw_dbg_cep(
@@ -1676,6 +1711,7 @@ int siw_accept(struct iw_cm_id *id, struct iw_cm_conn_param *params)
 	qp_attrs.sk = cep->sock;
 	if (cep->mpa.hdr.params.bits & MPA_RR_FLAG_CRC)
 		qp_attrs.flags = SIW_MPA_CRC;
+	cep->mpa.hdr.params.bits |= MPA_FPDU_LEN_64K;
 	qp_attrs.state = SIW_QP_STATE_RTS;
 
 	siw_dbg_cep(cep, "[QP%u]: moving to rts\n", qp_id(qp));
diff --git a/drivers/infiniband/sw/siw/siw_main.c b/drivers/infiniband/sw/siw/siw_main.c
index 05a92f997f60..28c256e52454 100644
--- a/drivers/infiniband/sw/siw/siw_main.c
+++ b/drivers/infiniband/sw/siw/siw_main.c
@@ -31,12 +31,6 @@ MODULE_LICENSE("Dual BSD/GPL");
 /* transmit from user buffer, if possible */
 const bool zcopy_tx = true;
 
-/* Restrict usage of GSO, if hardware peer iwarp is unable to process
- * large packets. try_gso = true lets siw try to use local GSO,
- * if peer agrees.  Not using GSO severly limits siw maximum tx bandwidth.
- */
-const bool try_gso;
-
 /* Attach siw also with loopback devices */
 const bool loopback_enabled = true;
 
diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c b/drivers/infiniband/sw/siw/siw_qp_tx.c
index 5d97bba0ce6d..d95bb0ed0d7c 100644
--- a/drivers/infiniband/sw/siw/siw_qp_tx.c
+++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
@@ -662,13 +662,17 @@ static void siw_update_tcpseg(struct siw_iwarp_tx *c_tx,
 {
 	struct tcp_sock *tp = tcp_sk(s->sk);
 
-	if (tp->gso_segs) {
-		if (c_tx->gso_seg_limit == 0)
-			c_tx->tcp_seglen = tp->mss_cache * tp->gso_segs;
-		else
+	if (tp->gso_segs && c_tx->large_fpdulen) {
+		if (tp->mss_cache >  c_tx->large_fpdulen) {
+			c_tx->tcp_seglen = c_tx->large_fpdulen;
+		} else {
+			u8 gso_seg_limit;
+			gso_seg_limit = c_tx->large_fpdulen / tp->mss_cache;
+
 			c_tx->tcp_seglen =
 				tp->mss_cache *
-				min_t(u16, c_tx->gso_seg_limit, tp->gso_segs);
+				min_t(u16, gso_seg_limit, tp->gso_segs);
+		}
 	} else {
 		c_tx->tcp_seglen = tp->mss_cache;
 	}
diff --git a/drivers/infiniband/sw/siw/siw_verbs.c b/drivers/infiniband/sw/siw/siw_verbs.c
index b18a677832e1..208557f91ff4 100644
--- a/drivers/infiniband/sw/siw/siw_verbs.c
+++ b/drivers/infiniband/sw/siw/siw_verbs.c
@@ -444,8 +444,7 @@ struct ib_qp *siw_create_qp(struct ib_pd *pd,
 	qp->attrs.sq_max_sges = attrs->cap.max_send_sge;
 	qp->attrs.rq_max_sges = attrs->cap.max_recv_sge;
 
-	/* Make those two tunables fixed for now. */
-	qp->tx_ctx.gso_seg_limit = 1;
+	/* Make this tunable fixed for now. */
 	qp->tx_ctx.zcopy_tx = zcopy_tx;
 
 	qp->attrs.state = SIW_QP_STATE_IDLE;

[-- Attachment #3: cxgb4.patch --]
[-- Type: text/plain, Size: 2388 bytes --]

diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c
index ee1182f..8941b64 100644
--- a/drivers/infiniband/hw/cxgb4/cm.c
+++ b/drivers/infiniband/hw/cxgb4/cm.c
@@ -135,6 +135,16 @@
 module_param(snd_win, int, 0644);
 MODULE_PARM_DESC(snd_win, "TCP send window in bytes (default=128KB)");
 
+/*
+ * Experimental large FPDU length support.
+ * This improves overall throughput while interop with SoftiWARP.
+ * Note that iw_cxgb4 advertises it's receiving capability only and ignores
+ * the remote peer's large FPDU length announcement, due to T6 HW limitaton.
+ */
+static int large_fpdulen;
+module_param(large_fpdulen, int, 0644);
+MODULE_PARM_DESC(large_fpdulen, "Experimental large FPDU length");
+
 static struct workqueue_struct *workq;
 
 static struct sk_buff_head rxq;
@@ -978,6 +988,12 @@ static int send_mpa_req(struct c4iw_ep *ep, struct sk_buff *skb,
 	mpa->flags = 0;
 	if (crc_enabled)
 		mpa->flags |= MPA_CRC;
+	if (large_fpdulen) {
+		if (CHELSIO_CHIP_VERSION(ep->com.dev->rdev.lldi.adapter_type) >=
+				CHELSIO_T6)
+			mpa->flags |= MPA_FPDU_LEN_16K;
+	}
+
 	if (markers_enabled) {
 		mpa->flags |= MPA_MARKERS;
 		ep->mpa_attr.recv_marker_enabled = 1;
@@ -1166,6 +1182,11 @@ static int send_mpa_reply(struct c4iw_ep *ep, const void *pdata, u8 plen)
 		mpa->flags |= MPA_CRC;
 	if (ep->mpa_attr.recv_marker_enabled)
 		mpa->flags |= MPA_MARKERS;
+	if (large_fpdulen) {
+		if (CHELSIO_CHIP_VERSION(ep->com.dev->rdev.lldi.adapter_type) >=
+				CHELSIO_T6)
+			mpa->flags |= MPA_FPDU_LEN_16K;
+	}
 	mpa->revision = ep->mpa_attr.version;
 	mpa->private_data_size = htons(plen);
 
diff --git a/drivers/infiniband/hw/cxgb4/iw_cxgb4.h b/drivers/infiniband/hw/cxgb4/iw_cxgb4.h
index 7d06b0f..051830e 100644
--- a/drivers/infiniband/hw/cxgb4/iw_cxgb4.h
+++ b/drivers/infiniband/hw/cxgb4/iw_cxgb4.h
@@ -688,6 +688,15 @@ enum c4iw_mmid_state {
 #define MPA_V2_RDMA_READ_RTR            0x4000
 #define MPA_V2_IRD_ORD_MASK             0x3FFF
 
+/* Following experimental bits should be in sync with SoftiWARP bits */
+#define MPA_FPDU_LEN_MASK 0x000c
+enum {
+	MPA_FPDU_LEN_DEFAULT = cpu_to_be16(0x0000),
+	MPA_FPDU_LEN_16K = cpu_to_be16(0x0400),
+	MPA_FPDU_LEN_32K = cpu_to_be16(0x0800),
+	MPA_FPDU_LEN_64K = cpu_to_be16(0x0c00)
+};
+
 #define c4iw_put_ep(ep) {						\
 	pr_debug("put_ep ep %p refcnt %d\n",		\
 		 ep, kref_read(&((ep)->kref)));				\

Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>
>From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>Date: 04/28/2020 10:01PM
>Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>nirranjan@chelsio.com
>Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
>negotiation of GSO usage.
>
>On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard Metzler
>wrote:
>Hi Bernard,
>
>The attached patches enables the GSO negotiation code in SIW with
>few modifications, and also allows hardware iwarp drivers to
>advertise
>their max length(in 16/32/64KB granularity) that they can accept.
>The logic is almost similar to how TCP SYN MSS announcements works
>while
>3-way handshake.
>
>Please see if this approach works better for softiwarp <=> hardiwarp
>case.
>
>Thanks,
>Krishna. 
>
Hi Krishna,

Thanks for providing this. I have a few comments:

It would be good if we can look at patches inlined in the
email body, as usual.

Before further discussing a complex solution as suggested
here, I would like to hear comments from other iWarp HW
vendors on their capabilities regarding GSO frame acceptance
and potential preferences. 

The extension proposed here goes beyond what I initially sent
as a proposed patch. From an siw point of view, it is straight
forward to select using GSO or not, depending on the iWarp peer
ability to process large frames. What is proposed here is a
end-to-end negotiation of the actual frame size.

A comment in the patch you sent suggests adding a module
parameter. Module parameters are deprecated, and I removed any
of those from siw when it went upstream. I don't think we can
rely on that mechanism.

siw has a compile time parameter (yes, that was a module
parameter) which can set the maximum tx frame size (in multiples
of MTU size). Any static setup of siw <-> Chelsio could make
use of that as a work around.

I wonder if it would be a better idea to look into an extension
of the rdma netlink protocol, which would allow setting driver
specific parameters per port, or even per QP.
I assume there are more potential use cases for driver private
extensions of the rdma netlink interface?

Thanks a lot!
Bernard.

Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

Hi Bernard,
Thanks for the review comments. Replied in line.

On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard Metzler wrote:
> 
> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >Date: 04/28/2020 10:01PM
> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >nirranjan@chelsio.com
> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
> >negotiation of GSO usage.
> >
> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard Metzler
> >wrote:
> >Hi Bernard,
> >
> >The attached patches enables the GSO negotiation code in SIW with
> >few modifications, and also allows hardware iwarp drivers to
> >advertise
> >their max length(in 16/32/64KB granularity) that they can accept.
> >The logic is almost similar to how TCP SYN MSS announcements works
> >while
> >3-way handshake.
> >
> >Please see if this approach works better for softiwarp <=> hardiwarp
> >case.
> >
> >Thanks,
> >Krishna. 
> >
> Hi Krishna,
> 
> Thanks for providing this. I have a few comments:
> 
> It would be good if we can look at patches inlined in the
> email body, as usual.
Sure, will do that henceforth.
> 
> Before further discussing a complex solution as suggested
> here, I would like to hear comments from other iWarp HW
> vendors on their capabilities regarding GSO frame acceptance
> and potential preferences. 
> 
> The extension proposed here goes beyond what I initially sent
> as a proposed patch. From an siw point of view, it is straight
> forward to select using GSO or not, depending on the iWarp peer
> ability to process large frames. What is proposed here is a
> end-to-end negotiation of the actual frame size.
> 
> A comment in the patch you sent suggests adding a module
> parameter. Module parameters are deprecated, and I removed any
> of those from siw when it went upstream. I don't think we can
> rely on that mechanism.
> 
> siw has a compile time parameter (yes, that was a module
> parameter) which can set the maximum tx frame size (in multiples
> of MTU size). Any static setup of siw <-> Chelsio could make
> use of that as a work around.
> 
> I wonder if it would be a better idea to look into an extension
> of the rdma netlink protocol, which would allow setting driver
> specific parameters per port, or even per QP.
> I assume there are more potential use cases for driver private
> extensions of the rdma netlink interface?

I think, the only problem with "configuring FPDU length via rdma
netlink" is the enduser might not feel comfortable in finding what adapter
is installed at the remote endpoint and what length it supports. Any
thoughts on simplify this?

Thanks,
Krishna.
> 
> Thanks a lot!
> Bernard.
> 

Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>
>From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>Date: 05/07/2020 01:07PM
>Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>nirranjan@chelsio.com
>Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e
>negotiation of GSO usage.
>
>Hi Bernard,
>Thanks for the review comments. Replied in line.
>
>On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard Metzler
>wrote:
>> 
>> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
>> 
>> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >Date: 04/28/2020 10:01PM
>> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> >nirranjan@chelsio.com
>> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
>> >negotiation of GSO usage.
>> >
>> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard
>Metzler
>> >wrote:
>> >Hi Bernard,
>> >
>> >The attached patches enables the GSO negotiation code in SIW with
>> >few modifications, and also allows hardware iwarp drivers to
>> >advertise
>> >their max length(in 16/32/64KB granularity) that they can accept.
>> >The logic is almost similar to how TCP SYN MSS announcements works
>> >while
>> >3-way handshake.
>> >
>> >Please see if this approach works better for softiwarp <=>
>hardiwarp
>> >case.
>> >
>> >Thanks,
>> >Krishna. 
>> >
>> Hi Krishna,
>> 
>> Thanks for providing this. I have a few comments:
>> 
>> It would be good if we can look at patches inlined in the
>> email body, as usual.
>Sure, will do that henceforth.
>> 
>> Before further discussing a complex solution as suggested
>> here, I would like to hear comments from other iWarp HW
>> vendors on their capabilities regarding GSO frame acceptance
>> and potential preferences. 
>> 
>> The extension proposed here goes beyond what I initially sent
>> as a proposed patch. From an siw point of view, it is straight
>> forward to select using GSO or not, depending on the iWarp peer
>> ability to process large frames. What is proposed here is a
>> end-to-end negotiation of the actual frame size.
>> 
>> A comment in the patch you sent suggests adding a module
>> parameter. Module parameters are deprecated, and I removed any
>> of those from siw when it went upstream. I don't think we can
>> rely on that mechanism.
>> 
>> siw has a compile time parameter (yes, that was a module
>> parameter) which can set the maximum tx frame size (in multiples
>> of MTU size). Any static setup of siw <-> Chelsio could make
>> use of that as a work around.
>> 
>> I wonder if it would be a better idea to look into an extension
>> of the rdma netlink protocol, which would allow setting driver
>> specific parameters per port, or even per QP.
>> I assume there are more potential use cases for driver private
>> extensions of the rdma netlink interface?
>
>I think, the only problem with "configuring FPDU length via rdma
>netlink" is the enduser might not feel comfortable in finding what
>adapter
>is installed at the remote endpoint and what length it supports. Any
>thoughts on simplify this?

Nope. This would be 'out of band' information.

So we seem to have 3 possible solutions to the problem:

(1) detect if the peer accepts FPDUs up to current GSO size,
this is what I initially proposed. (2) negotiate a max FPDU
size with the peer, this is what you are proposing, or (3)
explicitly set that max FPDU size per extended user interface.

My problem with (2) is the rather significant proprietary
extension of MPA, since spare bits code a max value negotiation.

I proposed (1) for its simplicity - just a single bit flag,
which de-/selects GSO size for FPDUs on TX. Since Chelsio
can handle _some_ larger (up to 16k, you said) sizes, (1)
might have to be extended to cap at hard coded max size.
Again, it would be good to know what other vendors limits
are.

Does 16k for siw  <-> Chelsio already yield a decent
performance win?

Thanks,
Bernard

Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard Metzler wrote:
> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >Date: 05/07/2020 01:07PM
> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >nirranjan@chelsio.com
> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e
> >negotiation of GSO usage.
> >
> >Hi Bernard,
> >Thanks for the review comments. Replied in line.
> >
> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard Metzler
> >wrote:
> >> 
> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> >> 
> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> >Date: 04/28/2020 10:01PM
> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> >nirranjan@chelsio.com
> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
> >> >negotiation of GSO usage.
> >> >
> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard
> >Metzler
> >> >wrote:
> >> >Hi Bernard,
> >> >
> >> >The attached patches enables the GSO negotiation code in SIW with
> >> >few modifications, and also allows hardware iwarp drivers to
> >> >advertise
> >> >their max length(in 16/32/64KB granularity) that they can accept.
> >> >The logic is almost similar to how TCP SYN MSS announcements works
> >> >while
> >> >3-way handshake.
> >> >
> >> >Please see if this approach works better for softiwarp <=>
> >hardiwarp
> >> >case.
> >> >
> >> >Thanks,
> >> >Krishna. 
> >> >
> >> Hi Krishna,
> >> 
> >> Thanks for providing this. I have a few comments:
> >> 
> >> It would be good if we can look at patches inlined in the
> >> email body, as usual.
> >Sure, will do that henceforth.
> >> 
> >> Before further discussing a complex solution as suggested
> >> here, I would like to hear comments from other iWarp HW
> >> vendors on their capabilities regarding GSO frame acceptance
> >> and potential preferences. 
> >> 
> >> The extension proposed here goes beyond what I initially sent
> >> as a proposed patch. From an siw point of view, it is straight
> >> forward to select using GSO or not, depending on the iWarp peer
> >> ability to process large frames. What is proposed here is a
> >> end-to-end negotiation of the actual frame size.
> >> 
> >> A comment in the patch you sent suggests adding a module
> >> parameter. Module parameters are deprecated, and I removed any
> >> of those from siw when it went upstream. I don't think we can
> >> rely on that mechanism.
> >> 
> >> siw has a compile time parameter (yes, that was a module
> >> parameter) which can set the maximum tx frame size (in multiples
> >> of MTU size). Any static setup of siw <-> Chelsio could make
> >> use of that as a work around.
> >> 
> >> I wonder if it would be a better idea to look into an extension
> >> of the rdma netlink protocol, which would allow setting driver
> >> specific parameters per port, or even per QP.
> >> I assume there are more potential use cases for driver private
> >> extensions of the rdma netlink interface?
> >
> >I think, the only problem with "configuring FPDU length via rdma
> >netlink" is the enduser might not feel comfortable in finding what
> >adapter
> >is installed at the remote endpoint and what length it supports. Any
> >thoughts on simplify this?
> 
> Nope. This would be 'out of band' information.
> 
> So we seem to have 3 possible solutions to the problem:
> 
> (1) detect if the peer accepts FPDUs up to current GSO size,
> this is what I initially proposed. (2) negotiate a max FPDU
> size with the peer, this is what you are proposing, or (3)
> explicitly set that max FPDU size per extended user interface.
> 
> My problem with (2) is the rather significant proprietary
> extension of MPA, since spare bits code a max value negotiation.
> 
> I proposed (1) for its simplicity - just a single bit flag,
> which de-/selects GSO size for FPDUs on TX. Since Chelsio
> can handle _some_ larger (up to 16k, you said) sizes, (1)
> might have to be extended to cap at hard coded max size.
> Again, it would be good to know what other vendors limits
> are.
> 
> Does 16k for siw  <-> Chelsio already yield a decent
> performance win?
yes, 3x performance gain with just 16K GSO, compared to GSO diabled
case. where MTU size is 1500.

Regarding the rdma netlink approach that you are suggesting, should it
be similar like below(?):

rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384, 102.5.5.6:32768


rdma link show iwp3s0f4/1 max_fpdu_len
        102.1.1.6:16384
        102.5.5.6:32768

where "102.1.1.6" is the destination IP address(such that the same max
fpdu length is taken for all the connections to this address/adapter).
And "16384" is max fdpu length.

> 
> Thanks,
> Bernard
> 

RE: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>
>From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>Date: 05/13/2020 05:50AM
>Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>nirranjan@chelsio.com
>Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
>e2e negotiation of GSO usage.
>
>On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard Metzler
>wrote:
>> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
>> 
>> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >Date: 05/07/2020 01:07PM
>> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> >nirranjan@chelsio.com
>> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e
>> >negotiation of GSO usage.
>> >
>> >Hi Bernard,
>> >Thanks for the review comments. Replied in line.
>> >
>> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard Metzler
>> >wrote:
>> >> 
>> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
>-----
>> >> 
>> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >> >Date: 04/28/2020 10:01PM
>> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> >> >nirranjan@chelsio.com
>> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
>> >> >negotiation of GSO usage.
>> >> >
>> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard
>> >Metzler
>> >> >wrote:
>> >> >Hi Bernard,
>> >> >
>> >> >The attached patches enables the GSO negotiation code in SIW
>with
>> >> >few modifications, and also allows hardware iwarp drivers to
>> >> >advertise
>> >> >their max length(in 16/32/64KB granularity) that they can
>accept.
>> >> >The logic is almost similar to how TCP SYN MSS announcements
>works
>> >> >while
>> >> >3-way handshake.
>> >> >
>> >> >Please see if this approach works better for softiwarp <=>
>> >hardiwarp
>> >> >case.
>> >> >
>> >> >Thanks,
>> >> >Krishna. 
>> >> >
>> >> Hi Krishna,
>> >> 
>> >> Thanks for providing this. I have a few comments:
>> >> 
>> >> It would be good if we can look at patches inlined in the
>> >> email body, as usual.
>> >Sure, will do that henceforth.
>> >> 
>> >> Before further discussing a complex solution as suggested
>> >> here, I would like to hear comments from other iWarp HW
>> >> vendors on their capabilities regarding GSO frame acceptance
>> >> and potential preferences. 
>> >> 
>> >> The extension proposed here goes beyond what I initially sent
>> >> as a proposed patch. From an siw point of view, it is straight
>> >> forward to select using GSO or not, depending on the iWarp peer
>> >> ability to process large frames. What is proposed here is a
>> >> end-to-end negotiation of the actual frame size.
>> >> 
>> >> A comment in the patch you sent suggests adding a module
>> >> parameter. Module parameters are deprecated, and I removed any
>> >> of those from siw when it went upstream. I don't think we can
>> >> rely on that mechanism.
>> >> 
>> >> siw has a compile time parameter (yes, that was a module
>> >> parameter) which can set the maximum tx frame size (in multiples
>> >> of MTU size). Any static setup of siw <-> Chelsio could make
>> >> use of that as a work around.
>> >> 
>> >> I wonder if it would be a better idea to look into an extension
>> >> of the rdma netlink protocol, which would allow setting driver
>> >> specific parameters per port, or even per QP.
>> >> I assume there are more potential use cases for driver private
>> >> extensions of the rdma netlink interface?
>> >
>> >I think, the only problem with "configuring FPDU length via rdma
>> >netlink" is the enduser might not feel comfortable in finding what
>> >adapter
>> >is installed at the remote endpoint and what length it supports.
>Any
>> >thoughts on simplify this?
>> 
>> Nope. This would be 'out of band' information.
>> 
>> So we seem to have 3 possible solutions to the problem:
>> 
>> (1) detect if the peer accepts FPDUs up to current GSO size,
>> this is what I initially proposed. (2) negotiate a max FPDU
>> size with the peer, this is what you are proposing, or (3)
>> explicitly set that max FPDU size per extended user interface.
>> 
>> My problem with (2) is the rather significant proprietary
>> extension of MPA, since spare bits code a max value negotiation.
>> 
>> I proposed (1) for its simplicity - just a single bit flag,
>> which de-/selects GSO size for FPDUs on TX. Since Chelsio
>> can handle _some_ larger (up to 16k, you said) sizes, (1)
>> might have to be extended to cap at hard coded max size.
>> Again, it would be good to know what other vendors limits
>> are.
>> 
>> Does 16k for siw  <-> Chelsio already yield a decent
>> performance win?
>yes, 3x performance gain with just 16K GSO, compared to GSO diabled
>case. where MTU size is 1500.
>

That is a lot. At the other hand, I would suggest to always
increase MTU size to max (9k) for adapters siw attaches to.
With a page size of 4k, anything below 4k MTU size hurts,
while 9k already packs two consecutive pages into one frame,
if aligned.

Would 16k still gain a significant performance win if we have
set max MTU size for the interface?

>Regarding the rdma netlink approach that you are suggesting, should
>it
>be similar like below(?):
>
>rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
>102.5.5.6:32768
>
>
>rdma link show iwp3s0f4/1 max_fpdu_len
>        102.1.1.6:16384
>        102.5.5.6:32768
>
>where "102.1.1.6" is the destination IP address(such that the same
>max
>fpdu length is taken for all the connections to this
>address/adapter).
>And "16384" is max fdpu length.
>
Yes, that would be one way of doing it. Unfortunately we
would end up with maintaining additional permanent in kernel
state per peer we ever configured.

So, would it make sense to combine it with the iwpmd,
which then may cache peers, while setting max_fpdu per
new connection? This would probably include extending the
proprietary port mapper protocol, to exchange local
preferences with the peer. Local capabilities might
be queried from the device (extending enum ib_mtu to
more than 4k, and using ibv_query_port()). And the
iw_cm_id to be extended to carry that extra parameter
down to the driver... Sounds complicated.

Thanks,
Bernard.

Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard Metzler wrote:
> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >Date: 05/13/2020 05:50AM
> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >nirranjan@chelsio.com
> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
> >e2e negotiation of GSO usage.
> >
> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard Metzler
> >wrote:
> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> >> 
> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> >Date: 05/07/2020 01:07PM
> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> >nirranjan@chelsio.com
> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e
> >> >negotiation of GSO usage.
> >> >
> >> >Hi Bernard,
> >> >Thanks for the review comments. Replied in line.
> >> >
> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard Metzler
> >> >wrote:
> >> >> 
> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> >-----
> >> >> 
> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> >> >Date: 04/28/2020 10:01PM
> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> >> >nirranjan@chelsio.com
> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental e2e
> >> >> >negotiation of GSO usage.
> >> >> >
> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000, Bernard
> >> >Metzler
> >> >> >wrote:
> >> >> >Hi Bernard,
> >> >> >
> >> >> >The attached patches enables the GSO negotiation code in SIW
> >with
> >> >> >few modifications, and also allows hardware iwarp drivers to
> >> >> >advertise
> >> >> >their max length(in 16/32/64KB granularity) that they can
> >accept.
> >> >> >The logic is almost similar to how TCP SYN MSS announcements
> >works
> >> >> >while
> >> >> >3-way handshake.
> >> >> >
> >> >> >Please see if this approach works better for softiwarp <=>
> >> >hardiwarp
> >> >> >case.
> >> >> >
> >> >> >Thanks,
> >> >> >Krishna. 
> >> >> >
> >> >> Hi Krishna,
> >> >> 
> >> >> Thanks for providing this. I have a few comments:
> >> >> 
> >> >> It would be good if we can look at patches inlined in the
> >> >> email body, as usual.
> >> >Sure, will do that henceforth.
> >> >> 
> >> >> Before further discussing a complex solution as suggested
> >> >> here, I would like to hear comments from other iWarp HW
> >> >> vendors on their capabilities regarding GSO frame acceptance
> >> >> and potential preferences. 
> >> >> 
> >> >> The extension proposed here goes beyond what I initially sent
> >> >> as a proposed patch. From an siw point of view, it is straight
> >> >> forward to select using GSO or not, depending on the iWarp peer
> >> >> ability to process large frames. What is proposed here is a
> >> >> end-to-end negotiation of the actual frame size.
> >> >> 
> >> >> A comment in the patch you sent suggests adding a module
> >> >> parameter. Module parameters are deprecated, and I removed any
> >> >> of those from siw when it went upstream. I don't think we can
> >> >> rely on that mechanism.
> >> >> 
> >> >> siw has a compile time parameter (yes, that was a module
> >> >> parameter) which can set the maximum tx frame size (in multiples
> >> >> of MTU size). Any static setup of siw <-> Chelsio could make
> >> >> use of that as a work around.
> >> >> 
> >> >> I wonder if it would be a better idea to look into an extension
> >> >> of the rdma netlink protocol, which would allow setting driver
> >> >> specific parameters per port, or even per QP.
> >> >> I assume there are more potential use cases for driver private
> >> >> extensions of the rdma netlink interface?
> >> >
> >> >I think, the only problem with "configuring FPDU length via rdma
> >> >netlink" is the enduser might not feel comfortable in finding what
> >> >adapter
> >> >is installed at the remote endpoint and what length it supports.
> >Any
> >> >thoughts on simplify this?
> >> 
> >> Nope. This would be 'out of band' information.
> >> 
> >> So we seem to have 3 possible solutions to the problem:
> >> 
> >> (1) detect if the peer accepts FPDUs up to current GSO size,
> >> this is what I initially proposed. (2) negotiate a max FPDU
> >> size with the peer, this is what you are proposing, or (3)
> >> explicitly set that max FPDU size per extended user interface.
> >> 
> >> My problem with (2) is the rather significant proprietary
> >> extension of MPA, since spare bits code a max value negotiation.
> >> 
> >> I proposed (1) for its simplicity - just a single bit flag,
> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
> >> might have to be extended to cap at hard coded max size.
> >> Again, it would be good to know what other vendors limits
> >> are.
> >> 
> >> Does 16k for siw  <-> Chelsio already yield a decent
> >> performance win?
> >yes, 3x performance gain with just 16K GSO, compared to GSO diabled
> >case. where MTU size is 1500.
> >
> 
> That is a lot. At the other hand, I would suggest to always
> increase MTU size to max (9k) for adapters siw attaches to.
> With a page size of 4k, anything below 4k MTU size hurts,
> while 9k already packs two consecutive pages into one frame,
> if aligned.
> 
> Would 16k still gain a significant performance win if we have
> set max MTU size for the interface?
> 
> >Regarding the rdma netlink approach that you are suggesting, should
> >it
> >be similar like below(?):
> >
> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
> >102.5.5.6:32768
> >
> >
> >rdma link show iwp3s0f4/1 max_fpdu_len
> >        102.1.1.6:16384
> >        102.5.5.6:32768
> >
> >where "102.1.1.6" is the destination IP address(such that the same
> >max
> >fpdu length is taken for all the connections to this
> >address/adapter).
> >And "16384" is max fdpu length.
> >
> Yes, that would be one way of doing it. Unfortunately we
> would end up with maintaining additional permanent in kernel
> state per peer we ever configured.
> 
> So, would it make sense to combine it with the iwpmd,
> which then may cache peers, while setting max_fpdu per
> new connection? This would probably include extending the
> proprietary port mapper protocol, to exchange local
> preferences with the peer. Local capabilities might
> be queried from the device (extending enum ib_mtu to
> more than 4k, and using ibv_query_port()). And the
> iw_cm_id to be extended to carry that extra parameter
> down to the driver... Sounds complicated.
If I understand you right, client/server advertises their Max FPDU len
in Res field of PMReq/PMAccept frames.
typedef struct iwpm_wire_msg {
        __u8    magic;
        __u8    pmtime;
        __be16  reserved;
Then after Portmapper negotiation, the fpdu len is propagated to SIW qp
strucutre from userspace iwpmd.
		
If we weigh up the pros and cons of using PortMapper Res field vs MPA
Res feild, then looks like using MPA is less complicated, considering
the lines of changes and modules invovled in changes. Not sure my
analysis is right here?

Between, looks like the existing SIW GSO code needs a logic to limit
"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in future to
best utilize 400G Ethernet, if Linux TCP stack has increased
GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit MPA len.

Thanks,
Krishna.

> 
> Thanks,
> Bernard.
> 

Re: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>
>From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>Date: 05/14/2020 01:17PM
>Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>nirranjan@chelsio.com
>Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
>e2e negotiation of GSO usage.
>
>On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard Metzler
>wrote:
>> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
>> 
>> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >Date: 05/13/2020 05:50AM
>> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> >nirranjan@chelsio.com
>> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
>> >e2e negotiation of GSO usage.
>> >
>> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard Metzler
>> >wrote:
>> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
>-----
>> >> 
>> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >> >Date: 05/07/2020 01:07PM
>> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> >> >nirranjan@chelsio.com
>> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental
>e2e
>> >> >negotiation of GSO usage.
>> >> >
>> >> >Hi Bernard,
>> >> >Thanks for the review comments. Replied in line.
>> >> >
>> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard
>Metzler
>> >> >wrote:
>> >> >> 
>> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
>> >-----
>> >> >> 
>> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >> >> >Date: 04/28/2020 10:01PM
>> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >> >> >mkalderon@marvell.com, aelior@marvell.com,
>dledford@redhat.com,
>> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
>bharat@chelsio.com,
>> >> >> >nirranjan@chelsio.com
>> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental
>e2e
>> >> >> >negotiation of GSO usage.
>> >> >> >
>> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000,
>Bernard
>> >> >Metzler
>> >> >> >wrote:
>> >> >> >Hi Bernard,
>> >> >> >
>> >> >> >The attached patches enables the GSO negotiation code in SIW
>> >with
>> >> >> >few modifications, and also allows hardware iwarp drivers to
>> >> >> >advertise
>> >> >> >their max length(in 16/32/64KB granularity) that they can
>> >accept.
>> >> >> >The logic is almost similar to how TCP SYN MSS announcements
>> >works
>> >> >> >while
>> >> >> >3-way handshake.
>> >> >> >
>> >> >> >Please see if this approach works better for softiwarp <=>
>> >> >hardiwarp
>> >> >> >case.
>> >> >> >
>> >> >> >Thanks,
>> >> >> >Krishna. 
>> >> >> >
>> >> >> Hi Krishna,
>> >> >> 
>> >> >> Thanks for providing this. I have a few comments:
>> >> >> 
>> >> >> It would be good if we can look at patches inlined in the
>> >> >> email body, as usual.
>> >> >Sure, will do that henceforth.
>> >> >> 
>> >> >> Before further discussing a complex solution as suggested
>> >> >> here, I would like to hear comments from other iWarp HW
>> >> >> vendors on their capabilities regarding GSO frame acceptance
>> >> >> and potential preferences. 
>> >> >> 
>> >> >> The extension proposed here goes beyond what I initially sent
>> >> >> as a proposed patch. From an siw point of view, it is
>straight
>> >> >> forward to select using GSO or not, depending on the iWarp
>peer
>> >> >> ability to process large frames. What is proposed here is a
>> >> >> end-to-end negotiation of the actual frame size.
>> >> >> 
>> >> >> A comment in the patch you sent suggests adding a module
>> >> >> parameter. Module parameters are deprecated, and I removed
>any
>> >> >> of those from siw when it went upstream. I don't think we can
>> >> >> rely on that mechanism.
>> >> >> 
>> >> >> siw has a compile time parameter (yes, that was a module
>> >> >> parameter) which can set the maximum tx frame size (in
>multiples
>> >> >> of MTU size). Any static setup of siw <-> Chelsio could make
>> >> >> use of that as a work around.
>> >> >> 
>> >> >> I wonder if it would be a better idea to look into an
>extension
>> >> >> of the rdma netlink protocol, which would allow setting
>driver
>> >> >> specific parameters per port, or even per QP.
>> >> >> I assume there are more potential use cases for driver
>private
>> >> >> extensions of the rdma netlink interface?
>> >> >
>> >> >I think, the only problem with "configuring FPDU length via
>rdma
>> >> >netlink" is the enduser might not feel comfortable in finding
>what
>> >> >adapter
>> >> >is installed at the remote endpoint and what length it
>supports.
>> >Any
>> >> >thoughts on simplify this?
>> >> 
>> >> Nope. This would be 'out of band' information.
>> >> 
>> >> So we seem to have 3 possible solutions to the problem:
>> >> 
>> >> (1) detect if the peer accepts FPDUs up to current GSO size,
>> >> this is what I initially proposed. (2) negotiate a max FPDU
>> >> size with the peer, this is what you are proposing, or (3)
>> >> explicitly set that max FPDU size per extended user interface.
>> >> 
>> >> My problem with (2) is the rather significant proprietary
>> >> extension of MPA, since spare bits code a max value negotiation.
>> >> 
>> >> I proposed (1) for its simplicity - just a single bit flag,
>> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
>> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
>> >> might have to be extended to cap at hard coded max size.
>> >> Again, it would be good to know what other vendors limits
>> >> are.
>> >> 
>> >> Does 16k for siw  <-> Chelsio already yield a decent
>> >> performance win?
>> >yes, 3x performance gain with just 16K GSO, compared to GSO
>diabled
>> >case. where MTU size is 1500.
>> >
>> 
>> That is a lot. At the other hand, I would suggest to always
>> increase MTU size to max (9k) for adapters siw attaches to.
>> With a page size of 4k, anything below 4k MTU size hurts,
>> while 9k already packs two consecutive pages into one frame,
>> if aligned.
>> 
>> Would 16k still gain a significant performance win if we have
>> set max MTU size for the interface?
>> 
>> >Regarding the rdma netlink approach that you are suggesting,
>should
>> >it
>> >be similar like below(?):
>> >
>> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
>> >102.5.5.6:32768
>> >
>> >
>> >rdma link show iwp3s0f4/1 max_fpdu_len
>> >        102.1.1.6:16384
>> >        102.5.5.6:32768
>> >
>> >where "102.1.1.6" is the destination IP address(such that the same
>> >max
>> >fpdu length is taken for all the connections to this
>> >address/adapter).
>> >And "16384" is max fdpu length.
>> >
>> Yes, that would be one way of doing it. Unfortunately we
>> would end up with maintaining additional permanent in kernel
>> state per peer we ever configured.
>> 
>> So, would it make sense to combine it with the iwpmd,
>> which then may cache peers, while setting max_fpdu per
>> new connection? This would probably include extending the
>> proprietary port mapper protocol, to exchange local
>> preferences with the peer. Local capabilities might
>> be queried from the device (extending enum ib_mtu to
>> more than 4k, and using ibv_query_port()). And the
>> iw_cm_id to be extended to carry that extra parameter
>> down to the driver... Sounds complicated.
>If I understand you right, client/server advertises their Max FPDU
>len
>in Res field of PMReq/PMAccept frames.
>typedef struct iwpm_wire_msg {
>        __u8    magic;
>        __u8    pmtime;
>        __be16  reserved;
>Then after Portmapper negotiation, the fpdu len is propagated to SIW
>qp
>strucutre from userspace iwpmd.
>		
>If we weigh up the pros and cons of using PortMapper Res field vs MPA
>Res feild, then looks like using MPA is less complicated, considering
>the lines of changes and modules invovled in changes. Not sure my
>analysis is right here?
>
One important difference IMHO is that one approach would touch an
established IETF communication protocol (MPA), the other a
proprietary application (iwpmd).


>Between, looks like the existing SIW GSO code needs a logic to limit
>"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in future
>to
>best utilize 400G Ethernet, if Linux TCP stack has increased
>GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit MPA
>len.
>
Isn't GSO bound to IP fragmentation?

Thanks,
Bernard

Re: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

On Thursday, May 05/14/20, 2020 at 13:07:33 +0000, Bernard Metzler wrote:
> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >Date: 05/14/2020 01:17PM
> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >nirranjan@chelsio.com
> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
> >e2e negotiation of GSO usage.
> >
> >On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard Metzler
> >wrote:
> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> >> 
> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> >Date: 05/13/2020 05:50AM
> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> >nirranjan@chelsio.com
> >> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
> >> >e2e negotiation of GSO usage.
> >> >
> >> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard Metzler
> >> >wrote:
> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> >-----
> >> >> 
> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> >> >Date: 05/07/2020 01:07PM
> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> >> >nirranjan@chelsio.com
> >> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental
> >e2e
> >> >> >negotiation of GSO usage.
> >> >> >
> >> >> >Hi Bernard,
> >> >> >Thanks for the review comments. Replied in line.
> >> >> >
> >> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard
> >Metzler
> >> >> >wrote:
> >> >> >> 
> >> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> >> >-----
> >> >> >> 
> >> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> >> >> >Date: 04/28/2020 10:01PM
> >> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> >> >> >mkalderon@marvell.com, aelior@marvell.com,
> >dledford@redhat.com,
> >> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
> >bharat@chelsio.com,
> >> >> >> >nirranjan@chelsio.com
> >> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental
> >e2e
> >> >> >> >negotiation of GSO usage.
> >> >> >> >
> >> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000,
> >Bernard
> >> >> >Metzler
> >> >> >> >wrote:
> >> >> >> >Hi Bernard,
> >> >> >> >
> >> >> >> >The attached patches enables the GSO negotiation code in SIW
> >> >with
> >> >> >> >few modifications, and also allows hardware iwarp drivers to
> >> >> >> >advertise
> >> >> >> >their max length(in 16/32/64KB granularity) that they can
> >> >accept.
> >> >> >> >The logic is almost similar to how TCP SYN MSS announcements
> >> >works
> >> >> >> >while
> >> >> >> >3-way handshake.
> >> >> >> >
> >> >> >> >Please see if this approach works better for softiwarp <=>
> >> >> >hardiwarp
> >> >> >> >case.
> >> >> >> >
> >> >> >> >Thanks,
> >> >> >> >Krishna. 
> >> >> >> >
> >> >> >> Hi Krishna,
> >> >> >> 
> >> >> >> Thanks for providing this. I have a few comments:
> >> >> >> 
> >> >> >> It would be good if we can look at patches inlined in the
> >> >> >> email body, as usual.
> >> >> >Sure, will do that henceforth.
> >> >> >> 
> >> >> >> Before further discussing a complex solution as suggested
> >> >> >> here, I would like to hear comments from other iWarp HW
> >> >> >> vendors on their capabilities regarding GSO frame acceptance
> >> >> >> and potential preferences. 
> >> >> >> 
> >> >> >> The extension proposed here goes beyond what I initially sent
> >> >> >> as a proposed patch. From an siw point of view, it is
> >straight
> >> >> >> forward to select using GSO or not, depending on the iWarp
> >peer
> >> >> >> ability to process large frames. What is proposed here is a
> >> >> >> end-to-end negotiation of the actual frame size.
> >> >> >> 
> >> >> >> A comment in the patch you sent suggests adding a module
> >> >> >> parameter. Module parameters are deprecated, and I removed
> >any
> >> >> >> of those from siw when it went upstream. I don't think we can
> >> >> >> rely on that mechanism.
> >> >> >> 
> >> >> >> siw has a compile time parameter (yes, that was a module
> >> >> >> parameter) which can set the maximum tx frame size (in
> >multiples
> >> >> >> of MTU size). Any static setup of siw <-> Chelsio could make
> >> >> >> use of that as a work around.
> >> >> >> 
> >> >> >> I wonder if it would be a better idea to look into an
> >extension
> >> >> >> of the rdma netlink protocol, which would allow setting
> >driver
> >> >> >> specific parameters per port, or even per QP.
> >> >> >> I assume there are more potential use cases for driver
> >private
> >> >> >> extensions of the rdma netlink interface?
> >> >> >
> >> >> >I think, the only problem with "configuring FPDU length via
> >rdma
> >> >> >netlink" is the enduser might not feel comfortable in finding
> >what
> >> >> >adapter
> >> >> >is installed at the remote endpoint and what length it
> >supports.
> >> >Any
> >> >> >thoughts on simplify this?
> >> >> 
> >> >> Nope. This would be 'out of band' information.
> >> >> 
> >> >> So we seem to have 3 possible solutions to the problem:
> >> >> 
> >> >> (1) detect if the peer accepts FPDUs up to current GSO size,
> >> >> this is what I initially proposed. (2) negotiate a max FPDU
> >> >> size with the peer, this is what you are proposing, or (3)
> >> >> explicitly set that max FPDU size per extended user interface.
> >> >> 
> >> >> My problem with (2) is the rather significant proprietary
> >> >> extension of MPA, since spare bits code a max value negotiation.
> >> >> 
> >> >> I proposed (1) for its simplicity - just a single bit flag,
> >> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
> >> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
> >> >> might have to be extended to cap at hard coded max size.
> >> >> Again, it would be good to know what other vendors limits
> >> >> are.
> >> >> 
> >> >> Does 16k for siw  <-> Chelsio already yield a decent
> >> >> performance win?
> >> >yes, 3x performance gain with just 16K GSO, compared to GSO
> >diabled
> >> >case. where MTU size is 1500.
> >> >
> >> 
> >> That is a lot. At the other hand, I would suggest to always
> >> increase MTU size to max (9k) for adapters siw attaches to.
> >> With a page size of 4k, anything below 4k MTU size hurts,
> >> while 9k already packs two consecutive pages into one frame,
> >> if aligned.
> >> 
> >> Would 16k still gain a significant performance win if we have
> >> set max MTU size for the interface?
Unfortunately no difference in throughput when MTU is 9K, for 16K FPDU.
Looks like TCP stack constructs GSO/TSO buffer in multiples of HW
MSS(tp->mss_cache). So, as 16K FPDU buffer is not a multiple of 9K, TCP
stack slices 16K buffer into 9K & 7K buffers before passing it to NIC
driver.
Thus no difference in perfromance as each tx packet to NIC cannot go
beyond 9K, when FPDU len is 16K.
> >> 
> >> >Regarding the rdma netlink approach that you are suggesting,
> >should
> >> >it
> >> >be similar like below(?):
> >> >
> >> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
> >> >102.5.5.6:32768
> >> >
> >> >
> >> >rdma link show iwp3s0f4/1 max_fpdu_len
> >> >        102.1.1.6:16384
> >> >        102.5.5.6:32768
> >> >
> >> >where "102.1.1.6" is the destination IP address(such that the same
> >> >max
> >> >fpdu length is taken for all the connections to this
> >> >address/adapter).
> >> >And "16384" is max fdpu length.
> >> >
> >> Yes, that would be one way of doing it. Unfortunately we
> >> would end up with maintaining additional permanent in kernel
> >> state per peer we ever configured.
> >> 
> >> So, would it make sense to combine it with the iwpmd,
> >> which then may cache peers, while setting max_fpdu per
> >> new connection? This would probably include extending the
> >> proprietary port mapper protocol, to exchange local
> >> preferences with the peer. Local capabilities might
> >> be queried from the device (extending enum ib_mtu to
> >> more than 4k, and using ibv_query_port()). And the
> >> iw_cm_id to be extended to carry that extra parameter
> >> down to the driver... Sounds complicated.
> >If I understand you right, client/server advertises their Max FPDU
> >len
> >in Res field of PMReq/PMAccept frames.
> >typedef struct iwpm_wire_msg {
> >        __u8    magic;
> >        __u8    pmtime;
> >        __be16  reserved;
> >Then after Portmapper negotiation, the fpdu len is propagated to SIW
> >qp
> >strucutre from userspace iwpmd.
> >		
> >If we weigh up the pros and cons of using PortMapper Res field vs MPA
> >Res feild, then looks like using MPA is less complicated, considering
> >the lines of changes and modules invovled in changes. Not sure my
> >analysis is right here?
> >
> One important difference IMHO is that one approach would touch an
> established IETF communication protocol (MPA), the other a
> proprietary application (iwpmd).
Ok, will explore more on iwpmd approach, may be prototyping this would help.
> 
> 
> >Between, looks like the existing SIW GSO code needs a logic to limit
> >"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in future
> >to
> >best utilize 400G Ethernet, if Linux TCP stack has increased
> >GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit MPA
> >len.
> >
> Isn't GSO bound to IP fragmentation?
Not sure. But I would say it's better we limit "c_tx->tcp_seglen"
somewhere to 64K-1 to avoid future risks.
> 
> Thanks,
> Bernard
> 

Re: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

Here is the rough prototype of iwpmd approach(only kernel part).
Please take a look.
diff --git a/drivers/infiniband/core/iwcm.c
b/drivers/infiniband/core/iwcm.c
index ade71823370f..ffe8d4dce45e 100644
--- a/drivers/infiniband/core/iwcm.c
+++ b/drivers/infiniband/core/iwcm.c
@@ -530,6 +530,12 @@ static int iw_cm_map(struct iw_cm_id *cm_id, bool
active)
        pm_msg.rem_addr = cm_id->remote_addr;
        pm_msg.flags = (cm_id->device->iw_driver_flags &
IW_F_NO_PORT_MAP) ?
                       IWPM_FLAGS_NO_PORT_MAP : 0;
+       ret = ib_query_qp(qp, &qp_attr, 0, &qp_init_attr);
+        if (ret)
+                return ret;
+       else
+               pm_msg.loc_fpdu_maxlen = qp_attr.loc_fpdu_maxlen;
+
        if (active)
                status = iwpm_add_and_query_mapping(&pm_msg,
                                                    RDMA_NL_IWCM);
@@ -544,6 +550,14 @@ static int iw_cm_map(struct iw_cm_id *cm_id, bool
active)
                                             &cm_id->remote_addr,
                                             &cm_id->m_remote_addr);
                }
+
+               if (pm_msg.rem_fpdu_maxlen) {
+                       struct ib_qp_attr qp_attr = {0};
+
+                       qp_attr.rem_fpdu_maxlen =
pm_msg.rem_fpdu_maxlen;
+                       ib_modify_qp(qp, &qp_attr, IB_QP_FPDU_MAXLEN);
+               }
+
        }

        return iwpm_create_mapinfo(&cm_id->local_addr,
diff --git a/drivers/infiniband/sw/siw/siw.h
b/drivers/infiniband/sw/siw/siw.h
index dba4535494ab..2c717f274dbf 100644
--- a/drivers/infiniband/sw/siw/siw.h
+++ b/drivers/infiniband/sw/siw/siw.h
@@ -279,6 +279,7 @@ struct siw_qp_attrs {
        enum siw_qp_flags flags;

        struct socket *sk;
+       u16 rem_fpdu_maxlen; /* max len of FPDU that remote node can
accept */
 };

 enum siw_tx_ctx {
@@ -415,7 +416,6 @@ struct siw_iwarp_tx {
        u8 orq_fence : 1; /* ORQ full or Send fenced */
        u8 in_syscall : 1; /* TX out of user context */
        u8 zcopy_tx : 1; /* Use TCP_SENDPAGE if possible */
-       u8 gso_seg_limit; /* Maximum segments for GSO, 0 = unbound */

        u16 fpdu_len; /* len of FPDU to tx */
        unsigned int tcp_seglen; /* remaining tcp seg space */
@@ -505,7 +505,6 @@ struct iwarp_msg_info {

 /* Global siw parameters. Currently set in siw_main.c */
 extern const bool zcopy_tx;
-extern const bool try_gso;
 extern const bool loopback_enabled;
 extern const bool mpa_crc_required;
 extern const bool mpa_crc_strict;
diff --git a/drivers/infiniband/sw/siw/siw_cm.c
b/drivers/infiniband/sw/siw/siw_cm.c
index 8c1931a57f4a..c240c430542d 100644
--- a/drivers/infiniband/sw/siw/siw_cm.c
+++ b/drivers/infiniband/sw/siw/siw_cm.c
@@ -750,10 +750,6 @@ static int siw_proc_mpareply(struct siw_cep *cep)

                return -ECONNRESET;
        }
-       if (try_gso && rep->params.bits & MPA_RR_FLAG_GSO_EXP) {
-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
-               qp->tx_ctx.gso_seg_limit = 0;
-       }
        if ((rep->params.bits & MPA_RR_FLAG_MARKERS) ||
            (mpa_crc_required && !(rep->params.bits & MPA_RR_FLAG_CRC))
||
            (mpa_crc_strict && !mpa_crc_required &&
@@ -1373,6 +1369,7 @@ int siw_connect(struct iw_cm_id *id, struct
iw_cm_conn_param *params)
                rv = -EINVAL;
                goto error;
        }
+
        if (v4)
                siw_dbg_qp(qp,
                           "pd_len %d, laddr %pI4 %d, raddr %pI4 %d\n",
@@ -1469,9 +1466,6 @@ int siw_connect(struct iw_cm_id *id, struct
iw_cm_conn_param *params)
        }
        __mpa_rr_set_revision(&cep->mpa.hdr.params.bits, version);

-       if (try_gso)
-               cep->mpa.hdr.params.bits |= MPA_RR_FLAG_GSO_EXP;
-
        if (mpa_crc_required)
                cep->mpa.hdr.params.bits |= MPA_RR_FLAG_CRC;

@@ -1594,6 +1588,7 @@ int siw_accept(struct iw_cm_id *id, struct
iw_cm_conn_param *params)

                return -EINVAL;
        }
+
        down_write(&qp->state_lock);
        if (qp->attrs.state > SIW_QP_STATE_RTR) {
                rv = -EINVAL;
@@ -1602,10 +1597,6 @@ int siw_accept(struct iw_cm_id *id, struct
iw_cm_conn_param *params)
        }
        siw_dbg_cep(cep, "[QP %d]\n", params->qpn);

-       if (try_gso && cep->mpa.hdr.params.bits & MPA_RR_FLAG_GSO_EXP) {
-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
-               qp->tx_ctx.gso_seg_limit = 0;
-       }
        if (params->ord > sdev->attrs.max_ord ||
            params->ird > sdev->attrs.max_ird) {
                siw_dbg_cep(
diff --git a/drivers/infiniband/sw/siw/siw_main.c
b/drivers/infiniband/sw/siw/siw_main.c
index 05a92f997f60..28c256e52454 100644
--- a/drivers/infiniband/sw/siw/siw_main.c
+++ b/drivers/infiniband/sw/siw/siw_main.c
@@ -31,12 +31,6 @@ MODULE_LICENSE("Dual BSD/GPL");
 /* transmit from user buffer, if possible */
 const bool zcopy_tx = true;

-/* Restrict usage of GSO, if hardware peer iwarp is unable to process
- * large packets. try_gso = true lets siw try to use local GSO,
- * if peer agrees.  Not using GSO severly limits siw maximum tx
  bandwidth.
- */
-const bool try_gso;
-
 /* Attach siw also with loopback devices */
 const bool loopback_enabled = true;

diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c
b/drivers/infiniband/sw/siw/siw_qp_tx.c
index 5d97bba0ce6d..2a9fa4efab60 100644
--- a/drivers/infiniband/sw/siw/siw_qp_tx.c
+++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
@@ -661,14 +661,19 @@ static void siw_update_tcpseg(struct siw_iwarp_tx
*c_tx,
                                     struct socket *s)
 {
        struct tcp_sock *tp = tcp_sk(s->sk);
+       struct siw_qp *qp =  container_of(c_tx, struct siw_qp, tx_ctx);

-       if (tp->gso_segs) {
-               if (c_tx->gso_seg_limit == 0)
-                       c_tx->tcp_seglen = tp->mss_cache * tp->gso_segs;
-               else
+       if (tp->gso_segs && qp->attrs.rem_fpdu_maxlen) {
+               if(tp->mss_cache >  qp->attrs.rem_fpdu_maxlen) {
+                       c_tx->tcp_seglen = qp->attrs.rem_fpdu_maxlen;
+               } else {
+                       u8 gso_seg_limit;
+                       gso_seg_limit = qp->attrs.rem_fpdu_maxlen /
+                                               tp->mss_cache;
                        c_tx->tcp_seglen =
                                tp->mss_cache *
-                               min_t(u16, c_tx->gso_seg_limit,
                                tp->gso_segs);
+                               min_t(u16, gso_seg_limit, tp->gso_segs);
+               }
        } else {
                c_tx->tcp_seglen = tp->mss_cache;
        }
diff --git a/drivers/infiniband/sw/siw/siw_verbs.c
b/drivers/infiniband/sw/siw/siw_verbs.c
index b18a677832e1..c5f40d3454f3 100644
--- a/drivers/infiniband/sw/siw/siw_verbs.c
+++ b/drivers/infiniband/sw/siw/siw_verbs.c
@@ -444,8 +444,7 @@ struct ib_qp *siw_create_qp(struct ib_pd *pd,
        qp->attrs.sq_max_sges = attrs->cap.max_send_sge;
        qp->attrs.rq_max_sges = attrs->cap.max_recv_sge;

-       /* Make those two tunables fixed for now. */
-       qp->tx_ctx.gso_seg_limit = 1;
+       /* Make this tunable fixed for now. */
        qp->tx_ctx.zcopy_tx = zcopy_tx;

        qp->attrs.state = SIW_QP_STATE_IDLE;
@@ -537,6 +536,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct
ib_qp_attr *qp_attr,
        qp_attr->cap.max_send_sge = qp->attrs.sq_max_sges;
        qp_attr->cap.max_recv_wr = qp->attrs.rq_size;
        qp_attr->cap.max_recv_sge = qp->attrs.rq_max_sges;
+       qp_attr->cap.loc_fpdu_maxlen =  SZ_64K - 1;
        qp_attr->path_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
        qp_attr->max_rd_atomic = qp->attrs.irq_size;
        qp_attr->max_dest_rd_atomic = qp->attrs.orq_size;
@@ -550,6 +550,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct
ib_qp_attr *qp_attr,
        qp_init_attr->recv_cq = base_qp->recv_cq;
        qp_init_attr->srq = base_qp->srq;

+       qp_init_attr->cap = qp_attr->cap;
        qp_init_attr->cap = qp_attr->cap;

        return 0;
@@ -589,6 +590,8 @@ int siw_verbs_modify_qp(struct ib_qp *base_qp,
struct ib_qp_attr *attr,

                siw_attr_mask |= SIW_QP_ATTR_STATE;
        }
+       if (attr_mask & IB_QP_FPDU_MAXLEN)
+                qp->attrs.rem_fpdu_maxlen = attr->rem_fpdu_maxlen;
        if (!siw_attr_mask)
                goto out;

diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index e7e733add99f..5bc3e3b9ea61 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -1054,6 +1054,8 @@ struct ib_qp_cap {
         * and MRs based on this.
         */
        u32     max_rdma_ctxs;
+       /* Maximum length of FPDU that the device at local node could
accept */
+       u16     loc_fpdu_maxlen;
 };

 enum ib_sig_type {
@@ -1210,6 +1212,7 @@ enum ib_qp_attr_mask {
        IB_QP_RESERVED3                 = (1<<23),
        IB_QP_RESERVED4                 = (1<<24),
        IB_QP_RATE_LIMIT                = (1<<25),
+       IB_QP_FPDU_MAXLEN               = (1<<26),
 };

 enum ib_qp_state {
@@ -1260,6 +1263,7 @@ struct ib_qp_attr {
        u8                      alt_port_num;
        u8                      alt_timeout;
        u32                     rate_limit;
+       u16                     rem_fpdu_maxlen; /* remote node's max
len cap */
 };

 enum ib_wr_opcode {
diff --git a/include/rdma/iw_portmap.h b/include/rdma/iw_portmap.h
index c89535047c42..af1bc798f709 100644
--- a/include/rdma/iw_portmap.h
+++ b/include/rdma/iw_portmap.h
@@ -61,6 +61,8 @@ struct iwpm_sa_data {
        struct sockaddr_storage mapped_loc_addr;
        struct sockaddr_storage rem_addr;
        struct sockaddr_storage mapped_rem_addr;
+       u16 loc_fpdu_maxlen;
+       u16 rem_fpdu_maxlen;
        u32 flags;
 };

On Friday, May 05/15/20, 2020 at 19:20:40 +0530, Krishnamraju Eraparaju wrote:
> On Thursday, May 05/14/20, 2020 at 13:07:33 +0000, Bernard Metzler wrote:
> > -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> > 
> > >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >Date: 05/14/2020 01:17PM
> > >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> > >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> > >nirranjan@chelsio.com
> > >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
> > >e2e negotiation of GSO usage.
> > >
> > >On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard Metzler
> > >wrote:
> > >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> > >> 
> > >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> >Date: 05/13/2020 05:50AM
> > >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> > >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> > >> >nirranjan@chelsio.com
> > >> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental
> > >> >e2e negotiation of GSO usage.
> > >> >
> > >> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard Metzler
> > >> >wrote:
> > >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> > >-----
> > >> >> 
> > >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> >> >Date: 05/07/2020 01:07PM
> > >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> >> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> > >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> > >> >> >nirranjan@chelsio.com
> > >> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw: Experimental
> > >e2e
> > >> >> >negotiation of GSO usage.
> > >> >> >
> > >> >> >Hi Bernard,
> > >> >> >Thanks for the review comments. Replied in line.
> > >> >> >
> > >> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard
> > >Metzler
> > >> >> >wrote:
> > >> >> >> 
> > >> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> > >> >-----
> > >> >> >> 
> > >> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> >> >> >Date: 04/28/2020 10:01PM
> > >> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> >> >> >mkalderon@marvell.com, aelior@marvell.com,
> > >dledford@redhat.com,
> > >> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
> > >bharat@chelsio.com,
> > >> >> >> >nirranjan@chelsio.com
> > >> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw: Experimental
> > >e2e
> > >> >> >> >negotiation of GSO usage.
> > >> >> >> >
> > >> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000,
> > >Bernard
> > >> >> >Metzler
> > >> >> >> >wrote:
> > >> >> >> >Hi Bernard,
> > >> >> >> >
> > >> >> >> >The attached patches enables the GSO negotiation code in SIW
> > >> >with
> > >> >> >> >few modifications, and also allows hardware iwarp drivers to
> > >> >> >> >advertise
> > >> >> >> >their max length(in 16/32/64KB granularity) that they can
> > >> >accept.
> > >> >> >> >The logic is almost similar to how TCP SYN MSS announcements
> > >> >works
> > >> >> >> >while
> > >> >> >> >3-way handshake.
> > >> >> >> >
> > >> >> >> >Please see if this approach works better for softiwarp <=>
> > >> >> >hardiwarp
> > >> >> >> >case.
> > >> >> >> >
> > >> >> >> >Thanks,
> > >> >> >> >Krishna. 
> > >> >> >> >
> > >> >> >> Hi Krishna,
> > >> >> >> 
> > >> >> >> Thanks for providing this. I have a few comments:
> > >> >> >> 
> > >> >> >> It would be good if we can look at patches inlined in the
> > >> >> >> email body, as usual.
> > >> >> >Sure, will do that henceforth.
> > >> >> >> 
> > >> >> >> Before further discussing a complex solution as suggested
> > >> >> >> here, I would like to hear comments from other iWarp HW
> > >> >> >> vendors on their capabilities regarding GSO frame acceptance
> > >> >> >> and potential preferences. 
> > >> >> >> 
> > >> >> >> The extension proposed here goes beyond what I initially sent
> > >> >> >> as a proposed patch. From an siw point of view, it is
> > >straight
> > >> >> >> forward to select using GSO or not, depending on the iWarp
> > >peer
> > >> >> >> ability to process large frames. What is proposed here is a
> > >> >> >> end-to-end negotiation of the actual frame size.
> > >> >> >> 
> > >> >> >> A comment in the patch you sent suggests adding a module
> > >> >> >> parameter. Module parameters are deprecated, and I removed
> > >any
> > >> >> >> of those from siw when it went upstream. I don't think we can
> > >> >> >> rely on that mechanism.
> > >> >> >> 
> > >> >> >> siw has a compile time parameter (yes, that was a module
> > >> >> >> parameter) which can set the maximum tx frame size (in
> > >multiples
> > >> >> >> of MTU size). Any static setup of siw <-> Chelsio could make
> > >> >> >> use of that as a work around.
> > >> >> >> 
> > >> >> >> I wonder if it would be a better idea to look into an
> > >extension
> > >> >> >> of the rdma netlink protocol, which would allow setting
> > >driver
> > >> >> >> specific parameters per port, or even per QP.
> > >> >> >> I assume there are more potential use cases for driver
> > >private
> > >> >> >> extensions of the rdma netlink interface?
> > >> >> >
> > >> >> >I think, the only problem with "configuring FPDU length via
> > >rdma
> > >> >> >netlink" is the enduser might not feel comfortable in finding
> > >what
> > >> >> >adapter
> > >> >> >is installed at the remote endpoint and what length it
> > >supports.
> > >> >Any
> > >> >> >thoughts on simplify this?
> > >> >> 
> > >> >> Nope. This would be 'out of band' information.
> > >> >> 
> > >> >> So we seem to have 3 possible solutions to the problem:
> > >> >> 
> > >> >> (1) detect if the peer accepts FPDUs up to current GSO size,
> > >> >> this is what I initially proposed. (2) negotiate a max FPDU
> > >> >> size with the peer, this is what you are proposing, or (3)
> > >> >> explicitly set that max FPDU size per extended user interface.
> > >> >> 
> > >> >> My problem with (2) is the rather significant proprietary
> > >> >> extension of MPA, since spare bits code a max value negotiation.
> > >> >> 
> > >> >> I proposed (1) for its simplicity - just a single bit flag,
> > >> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
> > >> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
> > >> >> might have to be extended to cap at hard coded max size.
> > >> >> Again, it would be good to know what other vendors limits
> > >> >> are.
> > >> >> 
> > >> >> Does 16k for siw  <-> Chelsio already yield a decent
> > >> >> performance win?
> > >> >yes, 3x performance gain with just 16K GSO, compared to GSO
> > >diabled
> > >> >case. where MTU size is 1500.
> > >> >
> > >> 
> > >> That is a lot. At the other hand, I would suggest to always
> > >> increase MTU size to max (9k) for adapters siw attaches to.
> > >> With a page size of 4k, anything below 4k MTU size hurts,
> > >> while 9k already packs two consecutive pages into one frame,
> > >> if aligned.
> > >> 
> > >> Would 16k still gain a significant performance win if we have
> > >> set max MTU size for the interface?
> Unfortunately no difference in throughput when MTU is 9K, for 16K FPDU.
> Looks like TCP stack constructs GSO/TSO buffer in multiples of HW
> MSS(tp->mss_cache). So, as 16K FPDU buffer is not a multiple of 9K, TCP
> stack slices 16K buffer into 9K & 7K buffers before passing it to NIC
> driver.
> Thus no difference in perfromance as each tx packet to NIC cannot go
> beyond 9K, when FPDU len is 16K.
> > >> 
> > >> >Regarding the rdma netlink approach that you are suggesting,
> > >should
> > >> >it
> > >> >be similar like below(?):
> > >> >
> > >> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
> > >> >102.5.5.6:32768
> > >> >
> > >> >
> > >> >rdma link show iwp3s0f4/1 max_fpdu_len
> > >> >        102.1.1.6:16384
> > >> >        102.5.5.6:32768
> > >> >
> > >> >where "102.1.1.6" is the destination IP address(such that the same
> > >> >max
> > >> >fpdu length is taken for all the connections to this
> > >> >address/adapter).
> > >> >And "16384" is max fdpu length.
> > >> >
> > >> Yes, that would be one way of doing it. Unfortunately we
> > >> would end up with maintaining additional permanent in kernel
> > >> state per peer we ever configured.
> > >> 
> > >> So, would it make sense to combine it with the iwpmd,
> > >> which then may cache peers, while setting max_fpdu per
> > >> new connection? This would probably include extending the
> > >> proprietary port mapper protocol, to exchange local
> > >> preferences with the peer. Local capabilities might
> > >> be queried from the device (extending enum ib_mtu to
> > >> more than 4k, and using ibv_query_port()). And the
> > >> iw_cm_id to be extended to carry that extra parameter
> > >> down to the driver... Sounds complicated.
> > >If I understand you right, client/server advertises their Max FPDU
> > >len
> > >in Res field of PMReq/PMAccept frames.
> > >typedef struct iwpm_wire_msg {
> > >        __u8    magic;
> > >        __u8    pmtime;
> > >        __be16  reserved;
> > >Then after Portmapper negotiation, the fpdu len is propagated to SIW
> > >qp
> > >strucutre from userspace iwpmd.
> > >		
> > >If we weigh up the pros and cons of using PortMapper Res field vs MPA
> > >Res feild, then looks like using MPA is less complicated, considering
> > >the lines of changes and modules invovled in changes. Not sure my
> > >analysis is right here?
> > >
> > One important difference IMHO is that one approach would touch an
> > established IETF communication protocol (MPA), the other a
> > proprietary application (iwpmd).
> Ok, will explore more on iwpmd approach, may be prototyping this would help.
> > 
> > 
> > >Between, looks like the existing SIW GSO code needs a logic to limit
> > >"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in future
> > >to
> > >best utilize 400G Ethernet, if Linux TCP stack has increased
> > >GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit MPA
> > >len.
> > >
> > Isn't GSO bound to IP fragmentation?
> Not sure. But I would say it's better we limit "c_tx->tcp_seglen"
> somewhere to 64K-1 to avoid future risks.
> > 
> > Thanks,
> > Bernard
> > 

RE: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>
>From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>Date: 05/15/2020 03:58PM
>Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>nirranjan@chelsio.com
>Subject: [EXTERNAL] Re: Re: Re: Re: [RFC PATCH] RDMA/siw:
>Experimental e2e negotiation of GSO usage.
>
>Here is the rough prototype of iwpmd approach(only kernel part).
>Please take a look.


This indeed looks like a possible solution, which would
not affect the wire protocol.

Before we move ahead with that story in any direction,
I would really really appreciate to hear what other
iWarp vendors have to say.

0) would other vendors care about better performance
   in a mixed hardware/software iwarp setting?

1) what are the capabilities of other adapters in that
   respect, e.g. what is the maximum FPDU length it
   can process?

2) would other adapters be able to send larger FPDUs
   than MTU size?

3) what would be the preferred solution - using spare
   MPA protocol bits to signal capabilities or
   extending the proprietary iwarp port mapper with that
   functionality?

Thanks very much!
Bernard.



>diff --git a/drivers/infiniband/core/iwcm.c
>b/drivers/infiniband/core/iwcm.c
>index ade71823370f..ffe8d4dce45e 100644
>--- a/drivers/infiniband/core/iwcm.c
>+++ b/drivers/infiniband/core/iwcm.c
>@@ -530,6 +530,12 @@ static int iw_cm_map(struct iw_cm_id *cm_id,
>bool
>active)
>        pm_msg.rem_addr = cm_id->remote_addr;
>        pm_msg.flags = (cm_id->device->iw_driver_flags &
>IW_F_NO_PORT_MAP) ?
>                       IWPM_FLAGS_NO_PORT_MAP : 0;
>+       ret = ib_query_qp(qp, &qp_attr, 0, &qp_init_attr);
>+        if (ret)
>+                return ret;
>+       else
>+               pm_msg.loc_fpdu_maxlen = qp_attr.loc_fpdu_maxlen;
>+
>        if (active)
>                status = iwpm_add_and_query_mapping(&pm_msg,
>                                                    RDMA_NL_IWCM);
>@@ -544,6 +550,14 @@ static int iw_cm_map(struct iw_cm_id *cm_id,
>bool
>active)
>                                             &cm_id->remote_addr,
>                                             &cm_id->m_remote_addr);
>                }
>+
>+               if (pm_msg.rem_fpdu_maxlen) {
>+                       struct ib_qp_attr qp_attr = {0};
>+
>+                       qp_attr.rem_fpdu_maxlen =
>pm_msg.rem_fpdu_maxlen;
>+                       ib_modify_qp(qp, &qp_attr,
>IB_QP_FPDU_MAXLEN);
>+               }
>+
>        }
>
>        return iwpm_create_mapinfo(&cm_id->local_addr,
>diff --git a/drivers/infiniband/sw/siw/siw.h
>b/drivers/infiniband/sw/siw/siw.h
>index dba4535494ab..2c717f274dbf 100644
>--- a/drivers/infiniband/sw/siw/siw.h
>+++ b/drivers/infiniband/sw/siw/siw.h
>@@ -279,6 +279,7 @@ struct siw_qp_attrs {
>        enum siw_qp_flags flags;
>
>        struct socket *sk;
>+       u16 rem_fpdu_maxlen; /* max len of FPDU that remote node can
>accept */
> };
>
> enum siw_tx_ctx {
>@@ -415,7 +416,6 @@ struct siw_iwarp_tx {
>        u8 orq_fence : 1; /* ORQ full or Send fenced */
>        u8 in_syscall : 1; /* TX out of user context */
>        u8 zcopy_tx : 1; /* Use TCP_SENDPAGE if possible */
>-       u8 gso_seg_limit; /* Maximum segments for GSO, 0 = unbound */
>
>        u16 fpdu_len; /* len of FPDU to tx */
>        unsigned int tcp_seglen; /* remaining tcp seg space */
>@@ -505,7 +505,6 @@ struct iwarp_msg_info {
>
> /* Global siw parameters. Currently set in siw_main.c */
> extern const bool zcopy_tx;
>-extern const bool try_gso;
> extern const bool loopback_enabled;
> extern const bool mpa_crc_required;
> extern const bool mpa_crc_strict;
>diff --git a/drivers/infiniband/sw/siw/siw_cm.c
>b/drivers/infiniband/sw/siw/siw_cm.c
>index 8c1931a57f4a..c240c430542d 100644
>--- a/drivers/infiniband/sw/siw/siw_cm.c
>+++ b/drivers/infiniband/sw/siw/siw_cm.c
>@@ -750,10 +750,6 @@ static int siw_proc_mpareply(struct siw_cep
>*cep)
>
>                return -ECONNRESET;
>        }
>-       if (try_gso && rep->params.bits & MPA_RR_FLAG_GSO_EXP) {
>-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
>-               qp->tx_ctx.gso_seg_limit = 0;
>-       }
>        if ((rep->params.bits & MPA_RR_FLAG_MARKERS) ||
>            (mpa_crc_required && !(rep->params.bits &
>MPA_RR_FLAG_CRC))
>||
>            (mpa_crc_strict && !mpa_crc_required &&
>@@ -1373,6 +1369,7 @@ int siw_connect(struct iw_cm_id *id, struct
>iw_cm_conn_param *params)
>                rv = -EINVAL;
>                goto error;
>        }
>+
>        if (v4)
>                siw_dbg_qp(qp,
>                           "pd_len %d, laddr %pI4 %d, raddr %pI4
>%d\n",
>@@ -1469,9 +1466,6 @@ int siw_connect(struct iw_cm_id *id, struct
>iw_cm_conn_param *params)
>        }
>        __mpa_rr_set_revision(&cep->mpa.hdr.params.bits, version);
>
>-       if (try_gso)
>-               cep->mpa.hdr.params.bits |= MPA_RR_FLAG_GSO_EXP;
>-
>        if (mpa_crc_required)
>                cep->mpa.hdr.params.bits |= MPA_RR_FLAG_CRC;
>
>@@ -1594,6 +1588,7 @@ int siw_accept(struct iw_cm_id *id, struct
>iw_cm_conn_param *params)
>
>                return -EINVAL;
>        }
>+
>        down_write(&qp->state_lock);
>        if (qp->attrs.state > SIW_QP_STATE_RTR) {
>                rv = -EINVAL;
>@@ -1602,10 +1597,6 @@ int siw_accept(struct iw_cm_id *id, struct
>iw_cm_conn_param *params)
>        }
>        siw_dbg_cep(cep, "[QP %d]\n", params->qpn);
>
>-       if (try_gso && cep->mpa.hdr.params.bits &
>MPA_RR_FLAG_GSO_EXP) {
>-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
>-               qp->tx_ctx.gso_seg_limit = 0;
>-       }
>        if (params->ord > sdev->attrs.max_ord ||
>            params->ird > sdev->attrs.max_ird) {
>                siw_dbg_cep(
>diff --git a/drivers/infiniband/sw/siw/siw_main.c
>b/drivers/infiniband/sw/siw/siw_main.c
>index 05a92f997f60..28c256e52454 100644
>--- a/drivers/infiniband/sw/siw/siw_main.c
>+++ b/drivers/infiniband/sw/siw/siw_main.c
>@@ -31,12 +31,6 @@ MODULE_LICENSE("Dual BSD/GPL");
> /* transmit from user buffer, if possible */
> const bool zcopy_tx = true;
>
>-/* Restrict usage of GSO, if hardware peer iwarp is unable to
>process
>- * large packets. try_gso = true lets siw try to use local GSO,
>- * if peer agrees.  Not using GSO severly limits siw maximum tx
>  bandwidth.
>- */
>-const bool try_gso;
>-
> /* Attach siw also with loopback devices */
> const bool loopback_enabled = true;
>
>diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c
>b/drivers/infiniband/sw/siw/siw_qp_tx.c
>index 5d97bba0ce6d..2a9fa4efab60 100644
>--- a/drivers/infiniband/sw/siw/siw_qp_tx.c
>+++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
>@@ -661,14 +661,19 @@ static void siw_update_tcpseg(struct
>siw_iwarp_tx
>*c_tx,
>                                     struct socket *s)
> {
>        struct tcp_sock *tp = tcp_sk(s->sk);
>+       struct siw_qp *qp =  container_of(c_tx, struct siw_qp,
>tx_ctx);
>
>-       if (tp->gso_segs) {
>-               if (c_tx->gso_seg_limit == 0)
>-                       c_tx->tcp_seglen = tp->mss_cache *
>tp->gso_segs;
>-               else
>+       if (tp->gso_segs && qp->attrs.rem_fpdu_maxlen) {
>+               if(tp->mss_cache >  qp->attrs.rem_fpdu_maxlen) {
>+                       c_tx->tcp_seglen = qp->attrs.rem_fpdu_maxlen;
>+               } else {
>+                       u8 gso_seg_limit;
>+                       gso_seg_limit = qp->attrs.rem_fpdu_maxlen /
>+                                               tp->mss_cache;
>                        c_tx->tcp_seglen =
>                                tp->mss_cache *
>-                               min_t(u16, c_tx->gso_seg_limit,
>                                tp->gso_segs);
>+                               min_t(u16, gso_seg_limit,
>tp->gso_segs);
>+               }
>        } else {
>                c_tx->tcp_seglen = tp->mss_cache;
>        }
>diff --git a/drivers/infiniband/sw/siw/siw_verbs.c
>b/drivers/infiniband/sw/siw/siw_verbs.c
>index b18a677832e1..c5f40d3454f3 100644
>--- a/drivers/infiniband/sw/siw/siw_verbs.c
>+++ b/drivers/infiniband/sw/siw/siw_verbs.c
>@@ -444,8 +444,7 @@ struct ib_qp *siw_create_qp(struct ib_pd *pd,
>        qp->attrs.sq_max_sges = attrs->cap.max_send_sge;
>        qp->attrs.rq_max_sges = attrs->cap.max_recv_sge;
>
>-       /* Make those two tunables fixed for now. */
>-       qp->tx_ctx.gso_seg_limit = 1;
>+       /* Make this tunable fixed for now. */
>        qp->tx_ctx.zcopy_tx = zcopy_tx;
>
>        qp->attrs.state = SIW_QP_STATE_IDLE;
>@@ -537,6 +536,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct
>ib_qp_attr *qp_attr,
>        qp_attr->cap.max_send_sge = qp->attrs.sq_max_sges;
>        qp_attr->cap.max_recv_wr = qp->attrs.rq_size;
>        qp_attr->cap.max_recv_sge = qp->attrs.rq_max_sges;
>+       qp_attr->cap.loc_fpdu_maxlen =  SZ_64K - 1;
>        qp_attr->path_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
>        qp_attr->max_rd_atomic = qp->attrs.irq_size;
>        qp_attr->max_dest_rd_atomic = qp->attrs.orq_size;
>@@ -550,6 +550,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct
>ib_qp_attr *qp_attr,
>        qp_init_attr->recv_cq = base_qp->recv_cq;
>        qp_init_attr->srq = base_qp->srq;
>
>+       qp_init_attr->cap = qp_attr->cap;
>        qp_init_attr->cap = qp_attr->cap;
>
>        return 0;
>@@ -589,6 +590,8 @@ int siw_verbs_modify_qp(struct ib_qp *base_qp,
>struct ib_qp_attr *attr,
>
>                siw_attr_mask |= SIW_QP_ATTR_STATE;
>        }
>+       if (attr_mask & IB_QP_FPDU_MAXLEN)
>+                qp->attrs.rem_fpdu_maxlen = attr->rem_fpdu_maxlen;
>        if (!siw_attr_mask)
>                goto out;
>
>diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
>index e7e733add99f..5bc3e3b9ea61 100644
>--- a/include/rdma/ib_verbs.h
>+++ b/include/rdma/ib_verbs.h
>@@ -1054,6 +1054,8 @@ struct ib_qp_cap {
>         * and MRs based on this.
>         */
>        u32     max_rdma_ctxs;
>+       /* Maximum length of FPDU that the device at local node could
>accept */
>+       u16     loc_fpdu_maxlen;
> };
>
> enum ib_sig_type {
>@@ -1210,6 +1212,7 @@ enum ib_qp_attr_mask {
>        IB_QP_RESERVED3                 = (1<<23),
>        IB_QP_RESERVED4                 = (1<<24),
>        IB_QP_RATE_LIMIT                = (1<<25),
>+       IB_QP_FPDU_MAXLEN               = (1<<26),
> };
>
> enum ib_qp_state {
>@@ -1260,6 +1263,7 @@ struct ib_qp_attr {
>        u8                      alt_port_num;
>        u8                      alt_timeout;
>        u32                     rate_limit;
>+       u16                     rem_fpdu_maxlen; /* remote node's max
>len cap */
> };
>
> enum ib_wr_opcode {
>diff --git a/include/rdma/iw_portmap.h b/include/rdma/iw_portmap.h
>index c89535047c42..af1bc798f709 100644
>--- a/include/rdma/iw_portmap.h
>+++ b/include/rdma/iw_portmap.h
>@@ -61,6 +61,8 @@ struct iwpm_sa_data {
>        struct sockaddr_storage mapped_loc_addr;
>        struct sockaddr_storage rem_addr;
>        struct sockaddr_storage mapped_rem_addr;
>+       u16 loc_fpdu_maxlen;
>+       u16 rem_fpdu_maxlen;
>        u32 flags;
> };
>
>On Friday, May 05/15/20, 2020 at 19:20:40 +0530, Krishnamraju
>Eraparaju wrote:
>> On Thursday, May 05/14/20, 2020 at 13:07:33 +0000, Bernard Metzler
>wrote:
>> > -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
>> > 
>> > >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> > >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> > >Date: 05/14/2020 01:17PM
>> > >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> > >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> > >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> > >nirranjan@chelsio.com
>> > >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw:
>Experimental
>> > >e2e negotiation of GSO usage.
>> > >
>> > >On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard
>Metzler
>> > >wrote:
>> > >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
>-----
>> > >> 
>> > >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> > >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> > >> >Date: 05/13/2020 05:50AM
>> > >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> > >> >mkalderon@marvell.com, aelior@marvell.com,
>dledford@redhat.com,
>> > >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> > >> >nirranjan@chelsio.com
>> > >> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw:
>Experimental
>> > >> >e2e negotiation of GSO usage.
>> > >> >
>> > >> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard
>Metzler
>> > >> >wrote:
>> > >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
>> > >-----
>> > >> >> 
>> > >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> > >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> > >> >> >Date: 05/07/2020 01:07PM
>> > >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> > >> >> >mkalderon@marvell.com, aelior@marvell.com,
>dledford@redhat.com,
>> > >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
>bharat@chelsio.com,
>> > >> >> >nirranjan@chelsio.com
>> > >> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw:
>Experimental
>> > >e2e
>> > >> >> >negotiation of GSO usage.
>> > >> >> >
>> > >> >> >Hi Bernard,
>> > >> >> >Thanks for the review comments. Replied in line.
>> > >> >> >
>> > >> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard
>> > >Metzler
>> > >> >> >wrote:
>> > >> >> >> 
>> > >> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com>
>wrote:
>> > >> >-----
>> > >> >> >> 
>> > >> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> > >> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> > >> >> >> >Date: 04/28/2020 10:01PM
>> > >> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> > >> >> >> >mkalderon@marvell.com, aelior@marvell.com,
>> > >dledford@redhat.com,
>> > >> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
>> > >bharat@chelsio.com,
>> > >> >> >> >nirranjan@chelsio.com
>> > >> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw:
>Experimental
>> > >e2e
>> > >> >> >> >negotiation of GSO usage.
>> > >> >> >> >
>> > >> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000,
>> > >Bernard
>> > >> >> >Metzler
>> > >> >> >> >wrote:
>> > >> >> >> >Hi Bernard,
>> > >> >> >> >
>> > >> >> >> >The attached patches enables the GSO negotiation code
>in SIW
>> > >> >with
>> > >> >> >> >few modifications, and also allows hardware iwarp
>drivers to
>> > >> >> >> >advertise
>> > >> >> >> >their max length(in 16/32/64KB granularity) that they
>can
>> > >> >accept.
>> > >> >> >> >The logic is almost similar to how TCP SYN MSS
>announcements
>> > >> >works
>> > >> >> >> >while
>> > >> >> >> >3-way handshake.
>> > >> >> >> >
>> > >> >> >> >Please see if this approach works better for softiwarp
><=>
>> > >> >> >hardiwarp
>> > >> >> >> >case.
>> > >> >> >> >
>> > >> >> >> >Thanks,
>> > >> >> >> >Krishna. 
>> > >> >> >> >
>> > >> >> >> Hi Krishna,
>> > >> >> >> 
>> > >> >> >> Thanks for providing this. I have a few comments:
>> > >> >> >> 
>> > >> >> >> It would be good if we can look at patches inlined in
>the
>> > >> >> >> email body, as usual.
>> > >> >> >Sure, will do that henceforth.
>> > >> >> >> 
>> > >> >> >> Before further discussing a complex solution as
>suggested
>> > >> >> >> here, I would like to hear comments from other iWarp HW
>> > >> >> >> vendors on their capabilities regarding GSO frame
>acceptance
>> > >> >> >> and potential preferences. 
>> > >> >> >> 
>> > >> >> >> The extension proposed here goes beyond what I initially
>sent
>> > >> >> >> as a proposed patch. From an siw point of view, it is
>> > >straight
>> > >> >> >> forward to select using GSO or not, depending on the
>iWarp
>> > >peer
>> > >> >> >> ability to process large frames. What is proposed here
>is a
>> > >> >> >> end-to-end negotiation of the actual frame size.
>> > >> >> >> 
>> > >> >> >> A comment in the patch you sent suggests adding a module
>> > >> >> >> parameter. Module parameters are deprecated, and I
>removed
>> > >any
>> > >> >> >> of those from siw when it went upstream. I don't think
>we can
>> > >> >> >> rely on that mechanism.
>> > >> >> >> 
>> > >> >> >> siw has a compile time parameter (yes, that was a module
>> > >> >> >> parameter) which can set the maximum tx frame size (in
>> > >multiples
>> > >> >> >> of MTU size). Any static setup of siw <-> Chelsio could
>make
>> > >> >> >> use of that as a work around.
>> > >> >> >> 
>> > >> >> >> I wonder if it would be a better idea to look into an
>> > >extension
>> > >> >> >> of the rdma netlink protocol, which would allow setting
>> > >driver
>> > >> >> >> specific parameters per port, or even per QP.
>> > >> >> >> I assume there are more potential use cases for driver
>> > >private
>> > >> >> >> extensions of the rdma netlink interface?
>> > >> >> >
>> > >> >> >I think, the only problem with "configuring FPDU length
>via
>> > >rdma
>> > >> >> >netlink" is the enduser might not feel comfortable in
>finding
>> > >what
>> > >> >> >adapter
>> > >> >> >is installed at the remote endpoint and what length it
>> > >supports.
>> > >> >Any
>> > >> >> >thoughts on simplify this?
>> > >> >> 
>> > >> >> Nope. This would be 'out of band' information.
>> > >> >> 
>> > >> >> So we seem to have 3 possible solutions to the problem:
>> > >> >> 
>> > >> >> (1) detect if the peer accepts FPDUs up to current GSO
>size,
>> > >> >> this is what I initially proposed. (2) negotiate a max FPDU
>> > >> >> size with the peer, this is what you are proposing, or (3)
>> > >> >> explicitly set that max FPDU size per extended user
>interface.
>> > >> >> 
>> > >> >> My problem with (2) is the rather significant proprietary
>> > >> >> extension of MPA, since spare bits code a max value
>negotiation.
>> > >> >> 
>> > >> >> I proposed (1) for its simplicity - just a single bit flag,
>> > >> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
>> > >> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
>> > >> >> might have to be extended to cap at hard coded max size.
>> > >> >> Again, it would be good to know what other vendors limits
>> > >> >> are.
>> > >> >> 
>> > >> >> Does 16k for siw  <-> Chelsio already yield a decent
>> > >> >> performance win?
>> > >> >yes, 3x performance gain with just 16K GSO, compared to GSO
>> > >diabled
>> > >> >case. where MTU size is 1500.
>> > >> >
>> > >> 
>> > >> That is a lot. At the other hand, I would suggest to always
>> > >> increase MTU size to max (9k) for adapters siw attaches to.
>> > >> With a page size of 4k, anything below 4k MTU size hurts,
>> > >> while 9k already packs two consecutive pages into one frame,
>> > >> if aligned.
>> > >> 
>> > >> Would 16k still gain a significant performance win if we have
>> > >> set max MTU size for the interface?
>> Unfortunately no difference in throughput when MTU is 9K, for 16K
>FPDU.
>> Looks like TCP stack constructs GSO/TSO buffer in multiples of HW
>> MSS(tp->mss_cache). So, as 16K FPDU buffer is not a multiple of 9K,
>TCP
>> stack slices 16K buffer into 9K & 7K buffers before passing it to
>NIC
>> driver.
>> Thus no difference in perfromance as each tx packet to NIC cannot
>go
>> beyond 9K, when FPDU len is 16K.
>> > >> 
>> > >> >Regarding the rdma netlink approach that you are suggesting,
>> > >should
>> > >> >it
>> > >> >be similar like below(?):
>> > >> >
>> > >> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
>> > >> >102.5.5.6:32768
>> > >> >
>> > >> >
>> > >> >rdma link show iwp3s0f4/1 max_fpdu_len
>> > >> >        102.1.1.6:16384
>> > >> >        102.5.5.6:32768
>> > >> >
>> > >> >where "102.1.1.6" is the destination IP address(such that the
>same
>> > >> >max
>> > >> >fpdu length is taken for all the connections to this
>> > >> >address/adapter).
>> > >> >And "16384" is max fdpu length.
>> > >> >
>> > >> Yes, that would be one way of doing it. Unfortunately we
>> > >> would end up with maintaining additional permanent in kernel
>> > >> state per peer we ever configured.
>> > >> 
>> > >> So, would it make sense to combine it with the iwpmd,
>> > >> which then may cache peers, while setting max_fpdu per
>> > >> new connection? This would probably include extending the
>> > >> proprietary port mapper protocol, to exchange local
>> > >> preferences with the peer. Local capabilities might
>> > >> be queried from the device (extending enum ib_mtu to
>> > >> more than 4k, and using ibv_query_port()). And the
>> > >> iw_cm_id to be extended to carry that extra parameter
>> > >> down to the driver... Sounds complicated.
>> > >If I understand you right, client/server advertises their Max
>FPDU
>> > >len
>> > >in Res field of PMReq/PMAccept frames.
>> > >typedef struct iwpm_wire_msg {
>> > >        __u8    magic;
>> > >        __u8    pmtime;
>> > >        __be16  reserved;
>> > >Then after Portmapper negotiation, the fpdu len is propagated to
>SIW
>> > >qp
>> > >strucutre from userspace iwpmd.
>> > >		
>> > >If we weigh up the pros and cons of using PortMapper Res field
>vs MPA
>> > >Res feild, then looks like using MPA is less complicated,
>considering
>> > >the lines of changes and modules invovled in changes. Not sure
>my
>> > >analysis is right here?
>> > >
>> > One important difference IMHO is that one approach would touch an
>> > established IETF communication protocol (MPA), the other a
>> > proprietary application (iwpmd).
>> Ok, will explore more on iwpmd approach, may be prototyping this
>would help.
>> > 
>> > 
>> > >Between, looks like the existing SIW GSO code needs a logic to
>limit
>> > >"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in
>future
>> > >to
>> > >best utilize 400G Ethernet, if Linux TCP stack has increased
>> > >GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit
>MPA
>> > >len.
>> > >
>> > Isn't GSO bound to IP fragmentation?
>> Not sure. But I would say it's better we limit "c_tx->tcp_seglen"
>> somewhere to 64K-1 to avoid future risks.
>> > 
>> > Thanks,
>> > Bernard
>> > 
>

Re: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Krishnamraju Eraparaju]

> Before we move ahead with that story in any direction,
> I would really really appreciate to hear what other
> iWarp vendors have to say.

Ok Bernard, will wait for other iWARP vendors to answer you questions. 


Thanks,
Krishna.
On Tuesday, May 05/26/20, 2020 at 13:57:11 +0000, Bernard Metzler wrote:
> 
> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >Date: 05/15/2020 03:58PM
> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >nirranjan@chelsio.com
> >Subject: [EXTERNAL] Re: Re: Re: Re: [RFC PATCH] RDMA/siw:
> >Experimental e2e negotiation of GSO usage.
> >
> >Here is the rough prototype of iwpmd approach(only kernel part).
> >Please take a look.
> 
> 
> This indeed looks like a possible solution, which would
> not affect the wire protocol.
> 
> Before we move ahead with that story in any direction,
> I would really really appreciate to hear what other
> iWarp vendors have to say.
> 
> 0) would other vendors care about better performance
>    in a mixed hardware/software iwarp setting?
> 
> 1) what are the capabilities of other adapters in that
>    respect, e.g. what is the maximum FPDU length it
>    can process?
> 
> 2) would other adapters be able to send larger FPDUs
>    than MTU size?
> 
> 3) what would be the preferred solution - using spare
>    MPA protocol bits to signal capabilities or
>    extending the proprietary iwarp port mapper with that
>    functionality?
> 
> Thanks very much!
> Bernard.
> 
> 
> 
> >diff --git a/drivers/infiniband/core/iwcm.c
> >b/drivers/infiniband/core/iwcm.c
> >index ade71823370f..ffe8d4dce45e 100644
> >--- a/drivers/infiniband/core/iwcm.c
> >+++ b/drivers/infiniband/core/iwcm.c
> >@@ -530,6 +530,12 @@ static int iw_cm_map(struct iw_cm_id *cm_id,
> >bool
> >active)
> >        pm_msg.rem_addr = cm_id->remote_addr;
> >        pm_msg.flags = (cm_id->device->iw_driver_flags &
> >IW_F_NO_PORT_MAP) ?
> >                       IWPM_FLAGS_NO_PORT_MAP : 0;
> >+       ret = ib_query_qp(qp, &qp_attr, 0, &qp_init_attr);
> >+        if (ret)
> >+                return ret;
> >+       else
> >+               pm_msg.loc_fpdu_maxlen = qp_attr.loc_fpdu_maxlen;
> >+
> >        if (active)
> >                status = iwpm_add_and_query_mapping(&pm_msg,
> >                                                    RDMA_NL_IWCM);
> >@@ -544,6 +550,14 @@ static int iw_cm_map(struct iw_cm_id *cm_id,
> >bool
> >active)
> >                                             &cm_id->remote_addr,
> >                                             &cm_id->m_remote_addr);
> >                }
> >+
> >+               if (pm_msg.rem_fpdu_maxlen) {
> >+                       struct ib_qp_attr qp_attr = {0};
> >+
> >+                       qp_attr.rem_fpdu_maxlen =
> >pm_msg.rem_fpdu_maxlen;
> >+                       ib_modify_qp(qp, &qp_attr,
> >IB_QP_FPDU_MAXLEN);
> >+               }
> >+
> >        }
> >
> >        return iwpm_create_mapinfo(&cm_id->local_addr,
> >diff --git a/drivers/infiniband/sw/siw/siw.h
> >b/drivers/infiniband/sw/siw/siw.h
> >index dba4535494ab..2c717f274dbf 100644
> >--- a/drivers/infiniband/sw/siw/siw.h
> >+++ b/drivers/infiniband/sw/siw/siw.h
> >@@ -279,6 +279,7 @@ struct siw_qp_attrs {
> >        enum siw_qp_flags flags;
> >
> >        struct socket *sk;
> >+       u16 rem_fpdu_maxlen; /* max len of FPDU that remote node can
> >accept */
> > };
> >
> > enum siw_tx_ctx {
> >@@ -415,7 +416,6 @@ struct siw_iwarp_tx {
> >        u8 orq_fence : 1; /* ORQ full or Send fenced */
> >        u8 in_syscall : 1; /* TX out of user context */
> >        u8 zcopy_tx : 1; /* Use TCP_SENDPAGE if possible */
> >-       u8 gso_seg_limit; /* Maximum segments for GSO, 0 = unbound */
> >
> >        u16 fpdu_len; /* len of FPDU to tx */
> >        unsigned int tcp_seglen; /* remaining tcp seg space */
> >@@ -505,7 +505,6 @@ struct iwarp_msg_info {
> >
> > /* Global siw parameters. Currently set in siw_main.c */
> > extern const bool zcopy_tx;
> >-extern const bool try_gso;
> > extern const bool loopback_enabled;
> > extern const bool mpa_crc_required;
> > extern const bool mpa_crc_strict;
> >diff --git a/drivers/infiniband/sw/siw/siw_cm.c
> >b/drivers/infiniband/sw/siw/siw_cm.c
> >index 8c1931a57f4a..c240c430542d 100644
> >--- a/drivers/infiniband/sw/siw/siw_cm.c
> >+++ b/drivers/infiniband/sw/siw/siw_cm.c
> >@@ -750,10 +750,6 @@ static int siw_proc_mpareply(struct siw_cep
> >*cep)
> >
> >                return -ECONNRESET;
> >        }
> >-       if (try_gso && rep->params.bits & MPA_RR_FLAG_GSO_EXP) {
> >-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
> >-               qp->tx_ctx.gso_seg_limit = 0;
> >-       }
> >        if ((rep->params.bits & MPA_RR_FLAG_MARKERS) ||
> >            (mpa_crc_required && !(rep->params.bits &
> >MPA_RR_FLAG_CRC))
> >||
> >            (mpa_crc_strict && !mpa_crc_required &&
> >@@ -1373,6 +1369,7 @@ int siw_connect(struct iw_cm_id *id, struct
> >iw_cm_conn_param *params)
> >                rv = -EINVAL;
> >                goto error;
> >        }
> >+
> >        if (v4)
> >                siw_dbg_qp(qp,
> >                           "pd_len %d, laddr %pI4 %d, raddr %pI4
> >%d\n",
> >@@ -1469,9 +1466,6 @@ int siw_connect(struct iw_cm_id *id, struct
> >iw_cm_conn_param *params)
> >        }
> >        __mpa_rr_set_revision(&cep->mpa.hdr.params.bits, version);
> >
> >-       if (try_gso)
> >-               cep->mpa.hdr.params.bits |= MPA_RR_FLAG_GSO_EXP;
> >-
> >        if (mpa_crc_required)
> >                cep->mpa.hdr.params.bits |= MPA_RR_FLAG_CRC;
> >
> >@@ -1594,6 +1588,7 @@ int siw_accept(struct iw_cm_id *id, struct
> >iw_cm_conn_param *params)
> >
> >                return -EINVAL;
> >        }
> >+
> >        down_write(&qp->state_lock);
> >        if (qp->attrs.state > SIW_QP_STATE_RTR) {
> >                rv = -EINVAL;
> >@@ -1602,10 +1597,6 @@ int siw_accept(struct iw_cm_id *id, struct
> >iw_cm_conn_param *params)
> >        }
> >        siw_dbg_cep(cep, "[QP %d]\n", params->qpn);
> >
> >-       if (try_gso && cep->mpa.hdr.params.bits &
> >MPA_RR_FLAG_GSO_EXP) {
> >-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
> >-               qp->tx_ctx.gso_seg_limit = 0;
> >-       }
> >        if (params->ord > sdev->attrs.max_ord ||
> >            params->ird > sdev->attrs.max_ird) {
> >                siw_dbg_cep(
> >diff --git a/drivers/infiniband/sw/siw/siw_main.c
> >b/drivers/infiniband/sw/siw/siw_main.c
> >index 05a92f997f60..28c256e52454 100644
> >--- a/drivers/infiniband/sw/siw/siw_main.c
> >+++ b/drivers/infiniband/sw/siw/siw_main.c
> >@@ -31,12 +31,6 @@ MODULE_LICENSE("Dual BSD/GPL");
> > /* transmit from user buffer, if possible */
> > const bool zcopy_tx = true;
> >
> >-/* Restrict usage of GSO, if hardware peer iwarp is unable to
> >process
> >- * large packets. try_gso = true lets siw try to use local GSO,
> >- * if peer agrees.  Not using GSO severly limits siw maximum tx
> >  bandwidth.
> >- */
> >-const bool try_gso;
> >-
> > /* Attach siw also with loopback devices */
> > const bool loopback_enabled = true;
> >
> >diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c
> >b/drivers/infiniband/sw/siw/siw_qp_tx.c
> >index 5d97bba0ce6d..2a9fa4efab60 100644
> >--- a/drivers/infiniband/sw/siw/siw_qp_tx.c
> >+++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
> >@@ -661,14 +661,19 @@ static void siw_update_tcpseg(struct
> >siw_iwarp_tx
> >*c_tx,
> >                                     struct socket *s)
> > {
> >        struct tcp_sock *tp = tcp_sk(s->sk);
> >+       struct siw_qp *qp =  container_of(c_tx, struct siw_qp,
> >tx_ctx);
> >
> >-       if (tp->gso_segs) {
> >-               if (c_tx->gso_seg_limit == 0)
> >-                       c_tx->tcp_seglen = tp->mss_cache *
> >tp->gso_segs;
> >-               else
> >+       if (tp->gso_segs && qp->attrs.rem_fpdu_maxlen) {
> >+               if(tp->mss_cache >  qp->attrs.rem_fpdu_maxlen) {
> >+                       c_tx->tcp_seglen = qp->attrs.rem_fpdu_maxlen;
> >+               } else {
> >+                       u8 gso_seg_limit;
> >+                       gso_seg_limit = qp->attrs.rem_fpdu_maxlen /
> >+                                               tp->mss_cache;
> >                        c_tx->tcp_seglen =
> >                                tp->mss_cache *
> >-                               min_t(u16, c_tx->gso_seg_limit,
> >                                tp->gso_segs);
> >+                               min_t(u16, gso_seg_limit,
> >tp->gso_segs);
> >+               }
> >        } else {
> >                c_tx->tcp_seglen = tp->mss_cache;
> >        }
> >diff --git a/drivers/infiniband/sw/siw/siw_verbs.c
> >b/drivers/infiniband/sw/siw/siw_verbs.c
> >index b18a677832e1..c5f40d3454f3 100644
> >--- a/drivers/infiniband/sw/siw/siw_verbs.c
> >+++ b/drivers/infiniband/sw/siw/siw_verbs.c
> >@@ -444,8 +444,7 @@ struct ib_qp *siw_create_qp(struct ib_pd *pd,
> >        qp->attrs.sq_max_sges = attrs->cap.max_send_sge;
> >        qp->attrs.rq_max_sges = attrs->cap.max_recv_sge;
> >
> >-       /* Make those two tunables fixed for now. */
> >-       qp->tx_ctx.gso_seg_limit = 1;
> >+       /* Make this tunable fixed for now. */
> >        qp->tx_ctx.zcopy_tx = zcopy_tx;
> >
> >        qp->attrs.state = SIW_QP_STATE_IDLE;
> >@@ -537,6 +536,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct
> >ib_qp_attr *qp_attr,
> >        qp_attr->cap.max_send_sge = qp->attrs.sq_max_sges;
> >        qp_attr->cap.max_recv_wr = qp->attrs.rq_size;
> >        qp_attr->cap.max_recv_sge = qp->attrs.rq_max_sges;
> >+       qp_attr->cap.loc_fpdu_maxlen =  SZ_64K - 1;
> >        qp_attr->path_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
> >        qp_attr->max_rd_atomic = qp->attrs.irq_size;
> >        qp_attr->max_dest_rd_atomic = qp->attrs.orq_size;
> >@@ -550,6 +550,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct
> >ib_qp_attr *qp_attr,
> >        qp_init_attr->recv_cq = base_qp->recv_cq;
> >        qp_init_attr->srq = base_qp->srq;
> >
> >+       qp_init_attr->cap = qp_attr->cap;
> >        qp_init_attr->cap = qp_attr->cap;
> >
> >        return 0;
> >@@ -589,6 +590,8 @@ int siw_verbs_modify_qp(struct ib_qp *base_qp,
> >struct ib_qp_attr *attr,
> >
> >                siw_attr_mask |= SIW_QP_ATTR_STATE;
> >        }
> >+       if (attr_mask & IB_QP_FPDU_MAXLEN)
> >+                qp->attrs.rem_fpdu_maxlen = attr->rem_fpdu_maxlen;
> >        if (!siw_attr_mask)
> >                goto out;
> >
> >diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> >index e7e733add99f..5bc3e3b9ea61 100644
> >--- a/include/rdma/ib_verbs.h
> >+++ b/include/rdma/ib_verbs.h
> >@@ -1054,6 +1054,8 @@ struct ib_qp_cap {
> >         * and MRs based on this.
> >         */
> >        u32     max_rdma_ctxs;
> >+       /* Maximum length of FPDU that the device at local node could
> >accept */
> >+       u16     loc_fpdu_maxlen;
> > };
> >
> > enum ib_sig_type {
> >@@ -1210,6 +1212,7 @@ enum ib_qp_attr_mask {
> >        IB_QP_RESERVED3                 = (1<<23),
> >        IB_QP_RESERVED4                 = (1<<24),
> >        IB_QP_RATE_LIMIT                = (1<<25),
> >+       IB_QP_FPDU_MAXLEN               = (1<<26),
> > };
> >
> > enum ib_qp_state {
> >@@ -1260,6 +1263,7 @@ struct ib_qp_attr {
> >        u8                      alt_port_num;
> >        u8                      alt_timeout;
> >        u32                     rate_limit;
> >+       u16                     rem_fpdu_maxlen; /* remote node's max
> >len cap */
> > };
> >
> > enum ib_wr_opcode {
> >diff --git a/include/rdma/iw_portmap.h b/include/rdma/iw_portmap.h
> >index c89535047c42..af1bc798f709 100644
> >--- a/include/rdma/iw_portmap.h
> >+++ b/include/rdma/iw_portmap.h
> >@@ -61,6 +61,8 @@ struct iwpm_sa_data {
> >        struct sockaddr_storage mapped_loc_addr;
> >        struct sockaddr_storage rem_addr;
> >        struct sockaddr_storage mapped_rem_addr;
> >+       u16 loc_fpdu_maxlen;
> >+       u16 rem_fpdu_maxlen;
> >        u32 flags;
> > };
> >
> >On Friday, May 05/15/20, 2020 at 19:20:40 +0530, Krishnamraju
> >Eraparaju wrote:
> >> On Thursday, May 05/14/20, 2020 at 13:07:33 +0000, Bernard Metzler
> >wrote:
> >> > -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> >> > 
> >> > >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> > >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> > >Date: 05/14/2020 01:17PM
> >> > >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> > >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >> > >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> > >nirranjan@chelsio.com
> >> > >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw:
> >Experimental
> >> > >e2e negotiation of GSO usage.
> >> > >
> >> > >On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard
> >Metzler
> >> > >wrote:
> >> > >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> >-----
> >> > >> 
> >> > >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> > >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> > >> >Date: 05/13/2020 05:50AM
> >> > >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> > >> >mkalderon@marvell.com, aelior@marvell.com,
> >dledford@redhat.com,
> >> > >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >> > >> >nirranjan@chelsio.com
> >> > >> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw:
> >Experimental
> >> > >> >e2e negotiation of GSO usage.
> >> > >> >
> >> > >> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard
> >Metzler
> >> > >> >wrote:
> >> > >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> >> > >-----
> >> > >> >> 
> >> > >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> > >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> > >> >> >Date: 05/07/2020 01:07PM
> >> > >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> > >> >> >mkalderon@marvell.com, aelior@marvell.com,
> >dledford@redhat.com,
> >> > >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
> >bharat@chelsio.com,
> >> > >> >> >nirranjan@chelsio.com
> >> > >> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw:
> >Experimental
> >> > >e2e
> >> > >> >> >negotiation of GSO usage.
> >> > >> >> >
> >> > >> >> >Hi Bernard,
> >> > >> >> >Thanks for the review comments. Replied in line.
> >> > >> >> >
> >> > >> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard
> >> > >Metzler
> >> > >> >> >wrote:
> >> > >> >> >> 
> >> > >> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >wrote:
> >> > >> >-----
> >> > >> >> >> 
> >> > >> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >> > >> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >> > >> >> >> >Date: 04/28/2020 10:01PM
> >> > >> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >> > >> >> >> >mkalderon@marvell.com, aelior@marvell.com,
> >> > >dledford@redhat.com,
> >> > >> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
> >> > >bharat@chelsio.com,
> >> > >> >> >> >nirranjan@chelsio.com
> >> > >> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw:
> >Experimental
> >> > >e2e
> >> > >> >> >> >negotiation of GSO usage.
> >> > >> >> >> >
> >> > >> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000,
> >> > >Bernard
> >> > >> >> >Metzler
> >> > >> >> >> >wrote:
> >> > >> >> >> >Hi Bernard,
> >> > >> >> >> >
> >> > >> >> >> >The attached patches enables the GSO negotiation code
> >in SIW
> >> > >> >with
> >> > >> >> >> >few modifications, and also allows hardware iwarp
> >drivers to
> >> > >> >> >> >advertise
> >> > >> >> >> >their max length(in 16/32/64KB granularity) that they
> >can
> >> > >> >accept.
> >> > >> >> >> >The logic is almost similar to how TCP SYN MSS
> >announcements
> >> > >> >works
> >> > >> >> >> >while
> >> > >> >> >> >3-way handshake.
> >> > >> >> >> >
> >> > >> >> >> >Please see if this approach works better for softiwarp
> ><=>
> >> > >> >> >hardiwarp
> >> > >> >> >> >case.
> >> > >> >> >> >
> >> > >> >> >> >Thanks,
> >> > >> >> >> >Krishna. 
> >> > >> >> >> >
> >> > >> >> >> Hi Krishna,
> >> > >> >> >> 
> >> > >> >> >> Thanks for providing this. I have a few comments:
> >> > >> >> >> 
> >> > >> >> >> It would be good if we can look at patches inlined in
> >the
> >> > >> >> >> email body, as usual.
> >> > >> >> >Sure, will do that henceforth.
> >> > >> >> >> 
> >> > >> >> >> Before further discussing a complex solution as
> >suggested
> >> > >> >> >> here, I would like to hear comments from other iWarp HW
> >> > >> >> >> vendors on their capabilities regarding GSO frame
> >acceptance
> >> > >> >> >> and potential preferences. 
> >> > >> >> >> 
> >> > >> >> >> The extension proposed here goes beyond what I initially
> >sent
> >> > >> >> >> as a proposed patch. From an siw point of view, it is
> >> > >straight
> >> > >> >> >> forward to select using GSO or not, depending on the
> >iWarp
> >> > >peer
> >> > >> >> >> ability to process large frames. What is proposed here
> >is a
> >> > >> >> >> end-to-end negotiation of the actual frame size.
> >> > >> >> >> 
> >> > >> >> >> A comment in the patch you sent suggests adding a module
> >> > >> >> >> parameter. Module parameters are deprecated, and I
> >removed
> >> > >any
> >> > >> >> >> of those from siw when it went upstream. I don't think
> >we can
> >> > >> >> >> rely on that mechanism.
> >> > >> >> >> 
> >> > >> >> >> siw has a compile time parameter (yes, that was a module
> >> > >> >> >> parameter) which can set the maximum tx frame size (in
> >> > >multiples
> >> > >> >> >> of MTU size). Any static setup of siw <-> Chelsio could
> >make
> >> > >> >> >> use of that as a work around.
> >> > >> >> >> 
> >> > >> >> >> I wonder if it would be a better idea to look into an
> >> > >extension
> >> > >> >> >> of the rdma netlink protocol, which would allow setting
> >> > >driver
> >> > >> >> >> specific parameters per port, or even per QP.
> >> > >> >> >> I assume there are more potential use cases for driver
> >> > >private
> >> > >> >> >> extensions of the rdma netlink interface?
> >> > >> >> >
> >> > >> >> >I think, the only problem with "configuring FPDU length
> >via
> >> > >rdma
> >> > >> >> >netlink" is the enduser might not feel comfortable in
> >finding
> >> > >what
> >> > >> >> >adapter
> >> > >> >> >is installed at the remote endpoint and what length it
> >> > >supports.
> >> > >> >Any
> >> > >> >> >thoughts on simplify this?
> >> > >> >> 
> >> > >> >> Nope. This would be 'out of band' information.
> >> > >> >> 
> >> > >> >> So we seem to have 3 possible solutions to the problem:
> >> > >> >> 
> >> > >> >> (1) detect if the peer accepts FPDUs up to current GSO
> >size,
> >> > >> >> this is what I initially proposed. (2) negotiate a max FPDU
> >> > >> >> size with the peer, this is what you are proposing, or (3)
> >> > >> >> explicitly set that max FPDU size per extended user
> >interface.
> >> > >> >> 
> >> > >> >> My problem with (2) is the rather significant proprietary
> >> > >> >> extension of MPA, since spare bits code a max value
> >negotiation.
> >> > >> >> 
> >> > >> >> I proposed (1) for its simplicity - just a single bit flag,
> >> > >> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
> >> > >> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
> >> > >> >> might have to be extended to cap at hard coded max size.
> >> > >> >> Again, it would be good to know what other vendors limits
> >> > >> >> are.
> >> > >> >> 
> >> > >> >> Does 16k for siw  <-> Chelsio already yield a decent
> >> > >> >> performance win?
> >> > >> >yes, 3x performance gain with just 16K GSO, compared to GSO
> >> > >diabled
> >> > >> >case. where MTU size is 1500.
> >> > >> >
> >> > >> 
> >> > >> That is a lot. At the other hand, I would suggest to always
> >> > >> increase MTU size to max (9k) for adapters siw attaches to.
> >> > >> With a page size of 4k, anything below 4k MTU size hurts,
> >> > >> while 9k already packs two consecutive pages into one frame,
> >> > >> if aligned.
> >> > >> 
> >> > >> Would 16k still gain a significant performance win if we have
> >> > >> set max MTU size for the interface?
> >> Unfortunately no difference in throughput when MTU is 9K, for 16K
> >FPDU.
> >> Looks like TCP stack constructs GSO/TSO buffer in multiples of HW
> >> MSS(tp->mss_cache). So, as 16K FPDU buffer is not a multiple of 9K,
> >TCP
> >> stack slices 16K buffer into 9K & 7K buffers before passing it to
> >NIC
> >> driver.
> >> Thus no difference in perfromance as each tx packet to NIC cannot
> >go
> >> beyond 9K, when FPDU len is 16K.
> >> > >> 
> >> > >> >Regarding the rdma netlink approach that you are suggesting,
> >> > >should
> >> > >> >it
> >> > >> >be similar like below(?):
> >> > >> >
> >> > >> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
> >> > >> >102.5.5.6:32768
> >> > >> >
> >> > >> >
> >> > >> >rdma link show iwp3s0f4/1 max_fpdu_len
> >> > >> >        102.1.1.6:16384
> >> > >> >        102.5.5.6:32768
> >> > >> >
> >> > >> >where "102.1.1.6" is the destination IP address(such that the
> >same
> >> > >> >max
> >> > >> >fpdu length is taken for all the connections to this
> >> > >> >address/adapter).
> >> > >> >And "16384" is max fdpu length.
> >> > >> >
> >> > >> Yes, that would be one way of doing it. Unfortunately we
> >> > >> would end up with maintaining additional permanent in kernel
> >> > >> state per peer we ever configured.
> >> > >> 
> >> > >> So, would it make sense to combine it with the iwpmd,
> >> > >> which then may cache peers, while setting max_fpdu per
> >> > >> new connection? This would probably include extending the
> >> > >> proprietary port mapper protocol, to exchange local
> >> > >> preferences with the peer. Local capabilities might
> >> > >> be queried from the device (extending enum ib_mtu to
> >> > >> more than 4k, and using ibv_query_port()). And the
> >> > >> iw_cm_id to be extended to carry that extra parameter
> >> > >> down to the driver... Sounds complicated.
> >> > >If I understand you right, client/server advertises their Max
> >FPDU
> >> > >len
> >> > >in Res field of PMReq/PMAccept frames.
> >> > >typedef struct iwpm_wire_msg {
> >> > >        __u8    magic;
> >> > >        __u8    pmtime;
> >> > >        __be16  reserved;
> >> > >Then after Portmapper negotiation, the fpdu len is propagated to
> >SIW
> >> > >qp
> >> > >strucutre from userspace iwpmd.
> >> > >		
> >> > >If we weigh up the pros and cons of using PortMapper Res field
> >vs MPA
> >> > >Res feild, then looks like using MPA is less complicated,
> >considering
> >> > >the lines of changes and modules invovled in changes. Not sure
> >my
> >> > >analysis is right here?
> >> > >
> >> > One important difference IMHO is that one approach would touch an
> >> > established IETF communication protocol (MPA), the other a
> >> > proprietary application (iwpmd).
> >> Ok, will explore more on iwpmd approach, may be prototyping this
> >would help.
> >> > 
> >> > 
> >> > >Between, looks like the existing SIW GSO code needs a logic to
> >limit
> >> > >"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in
> >future
> >> > >to
> >> > >best utilize 400G Ethernet, if Linux TCP stack has increased
> >> > >GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit
> >MPA
> >> > >len.
> >> > >
> >> > Isn't GSO bound to IP fragmentation?
> >> Not sure. But I would say it's better we limit "c_tx->tcp_seglen"
> >> somewhere to 64K-1 to avoid future risks.
> >> > 
> >> > Thanks,
> >> > Bernard
> >> > 
> >
> 

RE: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Michal Kalderon]

> From: linux-rdma-owner@vger.kernel.org <linux-rdma-
> owner@vger.kernel.org> On Behalf Of Krishnamraju Eraparaju
> 
> 
> > Before we move ahead with that story in any direction, I would really
> > really appreciate to hear what other iWarp vendors have to say.
> 
> Ok Bernard, will wait for other iWARP vendors to answer you questions.
Hi Bernard, Krishna, 

Currently our adapter supports only FPDU length < MTU, we do support Jumbo frames.
We could add support for this in the future, enabling any FPDU size, but this would be a SW based
Solution, not sure it will give us a performance boost. 

We think changing the wire protocol requires standardization. 
The port mapper seems like a better solution for OS specific.

Thanks,
Michal

> 
> 
> Thanks,
> Krishna.
> On Tuesday, May 05/26/20, 2020 at 13:57:11 +0000, Bernard Metzler wrote:
> >
> > -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> >
> > >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >Date: 05/15/2020 03:58PM
> > >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> > >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> > >nirranjan@chelsio.com
> > >Subject: [EXTERNAL] Re: Re: Re: Re: [RFC PATCH] RDMA/siw:
> > >Experimental e2e negotiation of GSO usage.
> > >
> > >Here is the rough prototype of iwpmd approach(only kernel part).
> > >Please take a look.
> >
> >
> > This indeed looks like a possible solution, which would not affect the
> > wire protocol.
> >
> > Before we move ahead with that story in any direction, I would really
> > really appreciate to hear what other iWarp vendors have to say.
> >
> > 0) would other vendors care about better performance
> >    in a mixed hardware/software iwarp setting?
> >
> > 1) what are the capabilities of other adapters in that
> >    respect, e.g. what is the maximum FPDU length it
> >    can process?
> >
> > 2) would other adapters be able to send larger FPDUs
> >    than MTU size?
> >
> > 3) what would be the preferred solution - using spare
> >    MPA protocol bits to signal capabilities or
> >    extending the proprietary iwarp port mapper with that
> >    functionality?
> >
> > Thanks very much!
> > Bernard.
> >
> >
> >
> > >diff --git a/drivers/infiniband/core/iwcm.c
> > >b/drivers/infiniband/core/iwcm.c index ade71823370f..ffe8d4dce45e
> > >100644
> > >--- a/drivers/infiniband/core/iwcm.c
> > >+++ b/drivers/infiniband/core/iwcm.c
> > >@@ -530,6 +530,12 @@ static int iw_cm_map(struct iw_cm_id *cm_id,
> > >bool
> > >active)
> > >        pm_msg.rem_addr = cm_id->remote_addr;
> > >        pm_msg.flags = (cm_id->device->iw_driver_flags &
> > >IW_F_NO_PORT_MAP) ?
> > >                       IWPM_FLAGS_NO_PORT_MAP : 0;
> > >+       ret = ib_query_qp(qp, &qp_attr, 0, &qp_init_attr);
> > >+        if (ret)
> > >+                return ret;
> > >+       else
> > >+               pm_msg.loc_fpdu_maxlen = qp_attr.loc_fpdu_maxlen;
> > >+
> > >        if (active)
> > >                status = iwpm_add_and_query_mapping(&pm_msg,
> > >                                                    RDMA_NL_IWCM); @@
> > >-544,6 +550,14 @@ static int iw_cm_map(struct iw_cm_id *cm_id, bool
> > >active)
> > >                                             &cm_id->remote_addr,
> > >                                             &cm_id->m_remote_addr);
> > >                }
> > >+
> > >+               if (pm_msg.rem_fpdu_maxlen) {
> > >+                       struct ib_qp_attr qp_attr = {0};
> > >+
> > >+                       qp_attr.rem_fpdu_maxlen =
> > >pm_msg.rem_fpdu_maxlen;
> > >+                       ib_modify_qp(qp, &qp_attr,
> > >IB_QP_FPDU_MAXLEN);
> > >+               }
> > >+
> > >        }
> > >
> > >        return iwpm_create_mapinfo(&cm_id->local_addr,
> > >diff --git a/drivers/infiniband/sw/siw/siw.h
> > >b/drivers/infiniband/sw/siw/siw.h
> > >index dba4535494ab..2c717f274dbf 100644
> > >--- a/drivers/infiniband/sw/siw/siw.h
> > >+++ b/drivers/infiniband/sw/siw/siw.h
> > >@@ -279,6 +279,7 @@ struct siw_qp_attrs {
> > >        enum siw_qp_flags flags;
> > >
> > >        struct socket *sk;
> > >+       u16 rem_fpdu_maxlen; /* max len of FPDU that remote node can
> > >accept */
> > > };
> > >
> > > enum siw_tx_ctx {
> > >@@ -415,7 +416,6 @@ struct siw_iwarp_tx {
> > >        u8 orq_fence : 1; /* ORQ full or Send fenced */
> > >        u8 in_syscall : 1; /* TX out of user context */
> > >        u8 zcopy_tx : 1; /* Use TCP_SENDPAGE if possible */
> > >-       u8 gso_seg_limit; /* Maximum segments for GSO, 0 = unbound */
> > >
> > >        u16 fpdu_len; /* len of FPDU to tx */
> > >        unsigned int tcp_seglen; /* remaining tcp seg space */ @@
> > >-505,7 +505,6 @@ struct iwarp_msg_info {
> > >
> > > /* Global siw parameters. Currently set in siw_main.c */  extern
> > >const bool zcopy_tx; -extern const bool try_gso;  extern const bool
> > >loopback_enabled;  extern const bool mpa_crc_required;  extern const
> > >bool mpa_crc_strict; diff --git a/drivers/infiniband/sw/siw/siw_cm.c
> > >b/drivers/infiniband/sw/siw/siw_cm.c
> > >index 8c1931a57f4a..c240c430542d 100644
> > >--- a/drivers/infiniband/sw/siw/siw_cm.c
> > >+++ b/drivers/infiniband/sw/siw/siw_cm.c
> > >@@ -750,10 +750,6 @@ static int siw_proc_mpareply(struct siw_cep
> > >*cep)
> > >
> > >                return -ECONNRESET;
> > >        }
> > >-       if (try_gso && rep->params.bits & MPA_RR_FLAG_GSO_EXP) {
> > >-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
> > >-               qp->tx_ctx.gso_seg_limit = 0;
> > >-       }
> > >        if ((rep->params.bits & MPA_RR_FLAG_MARKERS) ||
> > >            (mpa_crc_required && !(rep->params.bits &
> > >MPA_RR_FLAG_CRC))
> > >||
> > >            (mpa_crc_strict && !mpa_crc_required && @@ -1373,6
> > >+1369,7 @@ int siw_connect(struct iw_cm_id *id, struct
> > >iw_cm_conn_param *params)
> > >                rv = -EINVAL;
> > >                goto error;
> > >        }
> > >+
> > >        if (v4)
> > >                siw_dbg_qp(qp,
> > >                           "pd_len %d, laddr %pI4 %d, raddr %pI4
> > >%d\n", @@ -1469,9 +1466,6 @@ int siw_connect(struct iw_cm_id *id,
> > >struct iw_cm_conn_param *params)
> > >        }
> > >        __mpa_rr_set_revision(&cep->mpa.hdr.params.bits, version);
> > >
> > >-       if (try_gso)
> > >-               cep->mpa.hdr.params.bits |= MPA_RR_FLAG_GSO_EXP;
> > >-
> > >        if (mpa_crc_required)
> > >                cep->mpa.hdr.params.bits |= MPA_RR_FLAG_CRC;
> > >
> > >@@ -1594,6 +1588,7 @@ int siw_accept(struct iw_cm_id *id, struct
> > >iw_cm_conn_param *params)
> > >
> > >                return -EINVAL;
> > >        }
> > >+
> > >        down_write(&qp->state_lock);
> > >        if (qp->attrs.state > SIW_QP_STATE_RTR) {
> > >                rv = -EINVAL;
> > >@@ -1602,10 +1597,6 @@ int siw_accept(struct iw_cm_id *id, struct
> > >iw_cm_conn_param *params)
> > >        }
> > >        siw_dbg_cep(cep, "[QP %d]\n", params->qpn);
> > >
> > >-       if (try_gso && cep->mpa.hdr.params.bits &
> > >MPA_RR_FLAG_GSO_EXP) {
> > >-               siw_dbg_cep(cep, "peer allows GSO on TX\n");
> > >-               qp->tx_ctx.gso_seg_limit = 0;
> > >-       }
> > >        if (params->ord > sdev->attrs.max_ord ||
> > >            params->ird > sdev->attrs.max_ird) {
> > >                siw_dbg_cep(
> > >diff --git a/drivers/infiniband/sw/siw/siw_main.c
> > >b/drivers/infiniband/sw/siw/siw_main.c
> > >index 05a92f997f60..28c256e52454 100644
> > >--- a/drivers/infiniband/sw/siw/siw_main.c
> > >+++ b/drivers/infiniband/sw/siw/siw_main.c
> > >@@ -31,12 +31,6 @@ MODULE_LICENSE("Dual BSD/GPL");
> > > /* transmit from user buffer, if possible */  const bool zcopy_tx =
> > >true;
> > >
> > >-/* Restrict usage of GSO, if hardware peer iwarp is unable to
> > >process
> > >- * large packets. try_gso = true lets siw try to use local GSO,
> > >- * if peer agrees.  Not using GSO severly limits siw maximum tx
> > >  bandwidth.
> > >- */
> > >-const bool try_gso;
> > >-
> > > /* Attach siw also with loopback devices */  const bool
> > >loopback_enabled = true;
> > >
> > >diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c
> > >b/drivers/infiniband/sw/siw/siw_qp_tx.c
> > >index 5d97bba0ce6d..2a9fa4efab60 100644
> > >--- a/drivers/infiniband/sw/siw/siw_qp_tx.c
> > >+++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
> > >@@ -661,14 +661,19 @@ static void siw_update_tcpseg(struct
> > >siw_iwarp_tx *c_tx,
> > >                                     struct socket *s)  {
> > >        struct tcp_sock *tp = tcp_sk(s->sk);
> > >+       struct siw_qp *qp =  container_of(c_tx, struct siw_qp,
> > >tx_ctx);
> > >
> > >-       if (tp->gso_segs) {
> > >-               if (c_tx->gso_seg_limit == 0)
> > >-                       c_tx->tcp_seglen = tp->mss_cache *
> > >tp->gso_segs;
> > >-               else
> > >+       if (tp->gso_segs && qp->attrs.rem_fpdu_maxlen) {
> > >+               if(tp->mss_cache >  qp->attrs.rem_fpdu_maxlen) {
> > >+                       c_tx->tcp_seglen = qp->attrs.rem_fpdu_maxlen;
> > >+               } else {
> > >+                       u8 gso_seg_limit;
> > >+                       gso_seg_limit = qp->attrs.rem_fpdu_maxlen /
> > >+                                               tp->mss_cache;
> > >                        c_tx->tcp_seglen =
> > >                                tp->mss_cache *
> > >-                               min_t(u16, c_tx->gso_seg_limit,
> > >                                tp->gso_segs);
> > >+                               min_t(u16, gso_seg_limit,
> > >tp->gso_segs);
> > >+               }
> > >        } else {
> > >                c_tx->tcp_seglen = tp->mss_cache;
> > >        }
> > >diff --git a/drivers/infiniband/sw/siw/siw_verbs.c
> > >b/drivers/infiniband/sw/siw/siw_verbs.c
> > >index b18a677832e1..c5f40d3454f3 100644
> > >--- a/drivers/infiniband/sw/siw/siw_verbs.c
> > >+++ b/drivers/infiniband/sw/siw/siw_verbs.c
> > >@@ -444,8 +444,7 @@ struct ib_qp *siw_create_qp(struct ib_pd *pd,
> > >        qp->attrs.sq_max_sges = attrs->cap.max_send_sge;
> > >        qp->attrs.rq_max_sges = attrs->cap.max_recv_sge;
> > >
> > >-       /* Make those two tunables fixed for now. */
> > >-       qp->tx_ctx.gso_seg_limit = 1;
> > >+       /* Make this tunable fixed for now. */
> > >        qp->tx_ctx.zcopy_tx = zcopy_tx;
> > >
> > >        qp->attrs.state = SIW_QP_STATE_IDLE; @@ -537,6 +536,7 @@ int
> > >siw_query_qp(struct ib_qp *base_qp, struct ib_qp_attr *qp_attr,
> > >        qp_attr->cap.max_send_sge = qp->attrs.sq_max_sges;
> > >        qp_attr->cap.max_recv_wr = qp->attrs.rq_size;
> > >        qp_attr->cap.max_recv_sge = qp->attrs.rq_max_sges;
> > >+       qp_attr->cap.loc_fpdu_maxlen =  SZ_64K - 1;
> > >        qp_attr->path_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
> > >        qp_attr->max_rd_atomic = qp->attrs.irq_size;
> > >        qp_attr->max_dest_rd_atomic = qp->attrs.orq_size; @@ -550,6
> > >+550,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct ib_qp_attr
> > >*qp_attr,
> > >        qp_init_attr->recv_cq = base_qp->recv_cq;
> > >        qp_init_attr->srq = base_qp->srq;
> > >
> > >+       qp_init_attr->cap = qp_attr->cap;
> > >        qp_init_attr->cap = qp_attr->cap;
> > >
> > >        return 0;
> > >@@ -589,6 +590,8 @@ int siw_verbs_modify_qp(struct ib_qp *base_qp,
> > >struct ib_qp_attr *attr,
> > >
> > >                siw_attr_mask |= SIW_QP_ATTR_STATE;
> > >        }
> > >+       if (attr_mask & IB_QP_FPDU_MAXLEN)
> > >+                qp->attrs.rem_fpdu_maxlen = attr->rem_fpdu_maxlen;
> > >        if (!siw_attr_mask)
> > >                goto out;
> > >
> > >diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h index
> > >e7e733add99f..5bc3e3b9ea61 100644
> > >--- a/include/rdma/ib_verbs.h
> > >+++ b/include/rdma/ib_verbs.h
> > >@@ -1054,6 +1054,8 @@ struct ib_qp_cap {
> > >         * and MRs based on this.
> > >         */
> > >        u32     max_rdma_ctxs;
> > >+       /* Maximum length of FPDU that the device at local node could
> > >accept */
> > >+       u16     loc_fpdu_maxlen;
> > > };
> > >
> > > enum ib_sig_type {
> > >@@ -1210,6 +1212,7 @@ enum ib_qp_attr_mask {
> > >        IB_QP_RESERVED3                 = (1<<23),
> > >        IB_QP_RESERVED4                 = (1<<24),
> > >        IB_QP_RATE_LIMIT                = (1<<25),
> > >+       IB_QP_FPDU_MAXLEN               = (1<<26),
> > > };
> > >
> > > enum ib_qp_state {
> > >@@ -1260,6 +1263,7 @@ struct ib_qp_attr {
> > >        u8                      alt_port_num;
> > >        u8                      alt_timeout;
> > >        u32                     rate_limit;
> > >+       u16                     rem_fpdu_maxlen; /* remote node's max
> > >len cap */
> > > };
> > >
> > > enum ib_wr_opcode {
> > >diff --git a/include/rdma/iw_portmap.h b/include/rdma/iw_portmap.h
> > >index c89535047c42..af1bc798f709 100644
> > >--- a/include/rdma/iw_portmap.h
> > >+++ b/include/rdma/iw_portmap.h
> > >@@ -61,6 +61,8 @@ struct iwpm_sa_data {
> > >        struct sockaddr_storage mapped_loc_addr;
> > >        struct sockaddr_storage rem_addr;
> > >        struct sockaddr_storage mapped_rem_addr;
> > >+       u16 loc_fpdu_maxlen;
> > >+       u16 rem_fpdu_maxlen;
> > >        u32 flags;
> > > };
> > >
> > >On Friday, May 05/15/20, 2020 at 19:20:40 +0530, Krishnamraju
> > >Eraparaju wrote:
> > >> On Thursday, May 05/14/20, 2020 at 13:07:33 +0000, Bernard Metzler
> > >wrote:
> > >> > -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> > >> >
> > >> > >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> > >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> > >Date: 05/14/2020 01:17PM
> > >> > >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> > >mkalderon@marvell.com, aelior@marvell.com,
> dledford@redhat.com,
> > >> > >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> > >> > >nirranjan@chelsio.com
> > >> > >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw:
> > >Experimental
> > >> > >e2e negotiation of GSO usage.
> > >> > >
> > >> > >On Wednesday, May 05/13/20, 2020 at 11:25:23 +0000, Bernard
> > >Metzler
> > >> > >wrote:
> > >> > >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> > >-----
> > >> > >>
> > >> > >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> > >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> > >> >Date: 05/13/2020 05:50AM
> > >> > >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> > >> >mkalderon@marvell.com, aelior@marvell.com,
> > >dledford@redhat.com,
> > >> > >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> > >> > >> >nirranjan@chelsio.com
> > >> > >> >Subject: [EXTERNAL] Re: Re: Re: [RFC PATCH] RDMA/siw:
> > >Experimental
> > >> > >> >e2e negotiation of GSO usage.
> > >> > >> >
> > >> > >> >On Monday, May 05/11/20, 2020 at 15:28:47 +0000, Bernard
> > >Metzler
> > >> > >> >wrote:
> > >> > >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote:
> > >> > >-----
> > >> > >> >>
> > >> > >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> > >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> > >> >> >Date: 05/07/2020 01:07PM
> > >> > >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> > >> >> >mkalderon@marvell.com, aelior@marvell.com,
> > >dledford@redhat.com,
> > >> > >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
> > >bharat@chelsio.com,
> > >> > >> >> >nirranjan@chelsio.com
> > >> > >> >> >Subject: [EXTERNAL] Re: Re: [RFC PATCH] RDMA/siw:
> > >Experimental
> > >> > >e2e
> > >> > >> >> >negotiation of GSO usage.
> > >> > >> >> >
> > >> > >> >> >Hi Bernard,
> > >> > >> >> >Thanks for the review comments. Replied in line.
> > >> > >> >> >
> > >> > >> >> >On Tuesday, May 05/05/20, 2020 at 11:19:46 +0000, Bernard
> > >> > >Metzler
> > >> > >> >> >wrote:
> > >> > >> >> >>
> > >> > >> >> >> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >wrote:
> > >> > >> >-----
> > >> > >> >> >>
> > >> > >> >> >> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> > >> > >> >> >> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> > >> > >> >> >> >Date: 04/28/2020 10:01PM
> > >> > >> >> >> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> > >> > >> >> >> >mkalderon@marvell.com, aelior@marvell.com,
> > >> > >dledford@redhat.com,
> > >> > >> >> >> >jgg@ziepe.ca, linux-rdma@vger.kernel.org,
> > >> > >bharat@chelsio.com,
> > >> > >> >> >> >nirranjan@chelsio.com
> > >> > >> >> >> >Subject: [EXTERNAL] Re: [RFC PATCH] RDMA/siw:
> > >Experimental
> > >> > >e2e
> > >> > >> >> >> >negotiation of GSO usage.
> > >> > >> >> >> >
> > >> > >> >> >> >On Wednesday, April 04/15/20, 2020 at 11:59:21 +0000,
> > >> > >Bernard
> > >> > >> >> >Metzler
> > >> > >> >> >> >wrote:
> > >> > >> >> >> >Hi Bernard,
> > >> > >> >> >> >
> > >> > >> >> >> >The attached patches enables the GSO negotiation code
> > >in SIW
> > >> > >> >with
> > >> > >> >> >> >few modifications, and also allows hardware iwarp
> > >drivers to
> > >> > >> >> >> >advertise
> > >> > >> >> >> >their max length(in 16/32/64KB granularity) that they
> > >can
> > >> > >> >accept.
> > >> > >> >> >> >The logic is almost similar to how TCP SYN MSS
> > >announcements
> > >> > >> >works
> > >> > >> >> >> >while
> > >> > >> >> >> >3-way handshake.
> > >> > >> >> >> >
> > >> > >> >> >> >Please see if this approach works better for softiwarp
> > ><=>
> > >> > >> >> >hardiwarp
> > >> > >> >> >> >case.
> > >> > >> >> >> >
> > >> > >> >> >> >Thanks,
> > >> > >> >> >> >Krishna.
> > >> > >> >> >> >
> > >> > >> >> >> Hi Krishna,
> > >> > >> >> >>
> > >> > >> >> >> Thanks for providing this. I have a few comments:
> > >> > >> >> >>
> > >> > >> >> >> It would be good if we can look at patches inlined in
> > >the
> > >> > >> >> >> email body, as usual.
> > >> > >> >> >Sure, will do that henceforth.
> > >> > >> >> >>
> > >> > >> >> >> Before further discussing a complex solution as
> > >suggested
> > >> > >> >> >> here, I would like to hear comments from other iWarp HW
> > >> > >> >> >> vendors on their capabilities regarding GSO frame
> > >acceptance
> > >> > >> >> >> and potential preferences.
> > >> > >> >> >>
> > >> > >> >> >> The extension proposed here goes beyond what I initially
> > >sent
> > >> > >> >> >> as a proposed patch. From an siw point of view, it is
> > >> > >straight
> > >> > >> >> >> forward to select using GSO or not, depending on the
> > >iWarp
> > >> > >peer
> > >> > >> >> >> ability to process large frames. What is proposed here
> > >is a
> > >> > >> >> >> end-to-end negotiation of the actual frame size.
> > >> > >> >> >>
> > >> > >> >> >> A comment in the patch you sent suggests adding a module
> > >> > >> >> >> parameter. Module parameters are deprecated, and I
> > >removed
> > >> > >any
> > >> > >> >> >> of those from siw when it went upstream. I don't think
> > >we can
> > >> > >> >> >> rely on that mechanism.
> > >> > >> >> >>
> > >> > >> >> >> siw has a compile time parameter (yes, that was a module
> > >> > >> >> >> parameter) which can set the maximum tx frame size (in
> > >> > >multiples
> > >> > >> >> >> of MTU size). Any static setup of siw <-> Chelsio could
> > >make
> > >> > >> >> >> use of that as a work around.
> > >> > >> >> >>
> > >> > >> >> >> I wonder if it would be a better idea to look into an
> > >> > >extension
> > >> > >> >> >> of the rdma netlink protocol, which would allow setting
> > >> > >driver
> > >> > >> >> >> specific parameters per port, or even per QP.
> > >> > >> >> >> I assume there are more potential use cases for driver
> > >> > >private
> > >> > >> >> >> extensions of the rdma netlink interface?
> > >> > >> >> >
> > >> > >> >> >I think, the only problem with "configuring FPDU length
> > >via
> > >> > >rdma
> > >> > >> >> >netlink" is the enduser might not feel comfortable in
> > >finding
> > >> > >what
> > >> > >> >> >adapter
> > >> > >> >> >is installed at the remote endpoint and what length it
> > >> > >supports.
> > >> > >> >Any
> > >> > >> >> >thoughts on simplify this?
> > >> > >> >>
> > >> > >> >> Nope. This would be 'out of band' information.
> > >> > >> >>
> > >> > >> >> So we seem to have 3 possible solutions to the problem:
> > >> > >> >>
> > >> > >> >> (1) detect if the peer accepts FPDUs up to current GSO
> > >size,
> > >> > >> >> this is what I initially proposed. (2) negotiate a max FPDU
> > >> > >> >> size with the peer, this is what you are proposing, or (3)
> > >> > >> >> explicitly set that max FPDU size per extended user
> > >interface.
> > >> > >> >>
> > >> > >> >> My problem with (2) is the rather significant proprietary
> > >> > >> >> extension of MPA, since spare bits code a max value
> > >negotiation.
> > >> > >> >>
> > >> > >> >> I proposed (1) for its simplicity - just a single bit flag,
> > >> > >> >> which de-/selects GSO size for FPDUs on TX. Since Chelsio
> > >> > >> >> can handle _some_ larger (up to 16k, you said) sizes, (1)
> > >> > >> >> might have to be extended to cap at hard coded max size.
> > >> > >> >> Again, it would be good to know what other vendors limits
> > >> > >> >> are.
> > >> > >> >>
> > >> > >> >> Does 16k for siw  <-> Chelsio already yield a decent
> > >> > >> >> performance win?
> > >> > >> >yes, 3x performance gain with just 16K GSO, compared to GSO
> > >> > >diabled
> > >> > >> >case. where MTU size is 1500.
> > >> > >> >
> > >> > >>
> > >> > >> That is a lot. At the other hand, I would suggest to always
> > >> > >> increase MTU size to max (9k) for adapters siw attaches to.
> > >> > >> With a page size of 4k, anything below 4k MTU size hurts,
> > >> > >> while 9k already packs two consecutive pages into one frame,
> > >> > >> if aligned.
> > >> > >>
> > >> > >> Would 16k still gain a significant performance win if we have
> > >> > >> set max MTU size for the interface?
> > >> Unfortunately no difference in throughput when MTU is 9K, for 16K
> > >FPDU.
> > >> Looks like TCP stack constructs GSO/TSO buffer in multiples of HW
> > >> MSS(tp->mss_cache). So, as 16K FPDU buffer is not a multiple of 9K,
> > >TCP
> > >> stack slices 16K buffer into 9K & 7K buffers before passing it to
> > >NIC
> > >> driver.
> > >> Thus no difference in perfromance as each tx packet to NIC cannot
> > >go
> > >> beyond 9K, when FPDU len is 16K.
> > >> > >>
> > >> > >> >Regarding the rdma netlink approach that you are suggesting,
> > >> > >should
> > >> > >> >it
> > >> > >> >be similar like below(?):
> > >> > >> >
> > >> > >> >rdma link set iwp3s0f4/1 max_fpdu_len 102.1.1.6:16384,
> > >> > >> >102.5.5.6:32768
> > >> > >> >
> > >> > >> >
> > >> > >> >rdma link show iwp3s0f4/1 max_fpdu_len
> > >> > >> >        102.1.1.6:16384
> > >> > >> >        102.5.5.6:32768
> > >> > >> >
> > >> > >> >where "102.1.1.6" is the destination IP address(such that the
> > >same
> > >> > >> >max
> > >> > >> >fpdu length is taken for all the connections to this
> > >> > >> >address/adapter).
> > >> > >> >And "16384" is max fdpu length.
> > >> > >> >
> > >> > >> Yes, that would be one way of doing it. Unfortunately we would
> > >> > >> end up with maintaining additional permanent in kernel state
> > >> > >> per peer we ever configured.
> > >> > >>
> > >> > >> So, would it make sense to combine it with the iwpmd, which
> > >> > >> then may cache peers, while setting max_fpdu per new
> > >> > >> connection? This would probably include extending the
> > >> > >> proprietary port mapper protocol, to exchange local
> > >> > >> preferences with the peer. Local capabilities might be queried
> > >> > >> from the device (extending enum ib_mtu to more than 4k, and
> > >> > >> using ibv_query_port()). And the iw_cm_id to be extended to
> > >> > >> carry that extra parameter down to the driver... Sounds
> > >> > >> complicated.
> > >> > >If I understand you right, client/server advertises their Max
> > >FPDU
> > >> > >len
> > >> > >in Res field of PMReq/PMAccept frames.
> > >> > >typedef struct iwpm_wire_msg {
> > >> > >        __u8    magic;
> > >> > >        __u8    pmtime;
> > >> > >        __be16  reserved;
> > >> > >Then after Portmapper negotiation, the fpdu len is propagated to
> > >SIW
> > >> > >qp
> > >> > >strucutre from userspace iwpmd.
> > >> > >
> > >> > >If we weigh up the pros and cons of using PortMapper Res field
> > >vs MPA
> > >> > >Res feild, then looks like using MPA is less complicated,
> > >considering
> > >> > >the lines of changes and modules invovled in changes. Not sure
> > >my
> > >> > >analysis is right here?
> > >> > >
> > >> > One important difference IMHO is that one approach would touch an
> > >> > established IETF communication protocol (MPA), the other a
> > >> > proprietary application (iwpmd).
> > >> Ok, will explore more on iwpmd approach, may be prototyping this
> > >would help.
> > >> >
> > >> >
> > >> > >Between, looks like the existing SIW GSO code needs a logic to
> > >limit
> > >> > >"c_tx->tcp_seglen" to 64K-1, as MPA len is only 16bit. Say, in
> > >future
> > >> > >to
> > >> > >best utilize 400G Ethernet, if Linux TCP stack has increased
> > >> > >GSO_MAX_SIZE to 128K, then SIW will cast 18bit value to 16bit
> > >MPA
> > >> > >len.
> > >> > >
> > >> > Isn't GSO bound to IP fragmentation?
> > >> Not sure. But I would say it's better we limit "c_tx->tcp_seglen"
> > >> somewhere to 64K-1 to avoid future risks.
> > >> >
> > >> > Thanks,
> > >> > Bernard
> > >> >
> > >
> >

RE: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Saleem, Shiraz]

> Subject: RE: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation
> of GSO usage.
> 
> 
> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
> >Date: 05/15/2020 03:58PM
> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
> >nirranjan@chelsio.com
> >Subject: [EXTERNAL] Re: Re: Re: Re: [RFC PATCH] RDMA/siw:
> >Experimental e2e negotiation of GSO usage.
> >
> >Here is the rough prototype of iwpmd approach(only kernel part).
> >Please take a look.
> 
> 
> This indeed looks like a possible solution, which would not affect the wire
> protocol.
> 
> Before we move ahead with that story in any direction, I would really really
> appreciate to hear what other iWarp vendors have to say.
> 
> 0) would other vendors care about better performance
>    in a mixed hardware/software iwarp setting?
> 
> 1) what are the capabilities of other adapters in that
>    respect, e.g. what is the maximum FPDU length it
>    can process?
> 
> 2) would other adapters be able to send larger FPDUs
>    than MTU size?
> 
> 3) what would be the preferred solution - using spare
>    MPA protocol bits to signal capabilities or
>    extending the proprietary iwarp port mapper with that
>    functionality?
> 
> Thanks very much!
> Bernard.
> 

Hi Bernard -  If we receive larger FPDU than MTU its handled in software
and therefore is a hit on perf. We do support jumbo packets but we do not
transmit FPDUs greater than MTU size. I recommend we do not add
unspec'd bits into the MPA protocol for gso negotiation. netlink based
approach or iwpmd sounds more reasonable.

Hope this helps.

Shiraz

Re: RE: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e negotiation of GSO usage.

[Bernard Metzler]

-----"Saleem, Shiraz" <shiraz.saleem@intel.com> wrote: -----

>To: "Bernard Metzler" <BMT@zurich.ibm.com>, "Krishnamraju Eraparaju"
><krishna2@chelsio.com>
>From: "Saleem, Shiraz" <shiraz.saleem@intel.com>
>Date: 05/29/2020 05:21PM
>Cc: "Latif, Faisal" <faisal.latif@intel.com>, "mkalderon@marvell.com"
><mkalderon@marvell.com>, "aelior@marvell.com" <aelior@marvell.com>,
>"dledford@redhat.com" <dledford@redhat.com>, "jgg@ziepe.ca"
><jgg@ziepe.ca>, "linux-rdma@vger.kernel.org"
><linux-rdma@vger.kernel.org>, "bharat@chelsio.com"
><bharat@chelsio.com>, "nirranjan@chelsio.com" <nirranjan@chelsio.com>
>Subject: [EXTERNAL] RE: Re: Re: Re: [RFC PATCH] RDMA/siw:
>Experimental e2e negotiation of GSO usage.
>
>> Subject: RE: Re: Re: Re: [RFC PATCH] RDMA/siw: Experimental e2e
>negotiation
>> of GSO usage.
>> 
>> 
>> -----"Krishnamraju Eraparaju" <krishna2@chelsio.com> wrote: -----
>> 
>> >To: "Bernard Metzler" <BMT@zurich.ibm.com>
>> >From: "Krishnamraju Eraparaju" <krishna2@chelsio.com>
>> >Date: 05/15/2020 03:58PM
>> >Cc: faisal.latif@intel.com, shiraz.saleem@intel.com,
>> >mkalderon@marvell.com, aelior@marvell.com, dledford@redhat.com,
>> >jgg@ziepe.ca, linux-rdma@vger.kernel.org, bharat@chelsio.com,
>> >nirranjan@chelsio.com
>> >Subject: [EXTERNAL] Re: Re: Re: Re: [RFC PATCH] RDMA/siw:
>> >Experimental e2e negotiation of GSO usage.
>> >
>> >Here is the rough prototype of iwpmd approach(only kernel part).
>> >Please take a look.
>> 
>> 
>> This indeed looks like a possible solution, which would not affect
>the wire
>> protocol.
>> 
>> Before we move ahead with that story in any direction, I would
>really really
>> appreciate to hear what other iWarp vendors have to say.
>> 
>> 0) would other vendors care about better performance
>>    in a mixed hardware/software iwarp setting?
>> 
>> 1) what are the capabilities of other adapters in that
>>    respect, e.g. what is the maximum FPDU length it
>>    can process?
>> 
>> 2) would other adapters be able to send larger FPDUs
>>    than MTU size?
>> 
>> 3) what would be the preferred solution - using spare
>>    MPA protocol bits to signal capabilities or
>>    extending the proprietary iwarp port mapper with that
>>    functionality?
>> 
>> Thanks very much!
>> Bernard.
>> 
>
>Hi Bernard -  If we receive larger FPDU than MTU its handled in
>software
>and therefore is a hit on perf. We do support jumbo packets but we do
>not
>transmit FPDUs greater than MTU size. I recommend we do not add
>unspec'd bits into the MPA protocol for gso negotiation. netlink
>based
>approach or iwpmd sounds more reasonable.
>
>Hope this helps.
>
It does!

Many thanks,
Bernard.
>Shiraz
>
>