[PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[Ka-Cheong Poon]

Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
of contiguous DMA coherent memory to store struct rds_header for
sending/receiving packets.  The memory allocated is then partitioned
into struct rds_header.  This is not necessary and can be costly at
times when memory is fragmented.  Instead, RDS should use the DMA
memory pool interface to handle this.

Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
---
 net/rds/ib.c      |  10 +++-
 net/rds/ib.h      |  15 +++--
 net/rds/ib_cm.c   | 166 +++++++++++++++++++++++++++++++++++++++---------------
 net/rds/ib_recv.c |   8 +--
 net/rds/ib_send.c |  15 +++--
 5 files changed, 153 insertions(+), 61 deletions(-)

diff --git a/net/rds/ib.c b/net/rds/ib.c
index 45acab2..01dc189 100644
--- a/net/rds/ib.c
+++ b/net/rds/ib.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -107,6 +107,8 @@ static void rds_ib_dev_free(struct work_struct *work)
 		rds_ib_destroy_mr_pool(rds_ibdev->mr_1m_pool);
 	if (rds_ibdev->pd)
 		ib_dealloc_pd(rds_ibdev->pd);
+	if (rds_ibdev->rid_hdrs_pool)
+		dma_pool_destroy(rds_ibdev->rid_hdrs_pool);
 
 	list_for_each_entry_safe(i_ipaddr, i_next, &rds_ibdev->ipaddr_list, list) {
 		list_del(&i_ipaddr->list);
@@ -179,6 +181,12 @@ static void rds_ib_add_one(struct ib_device *device)
 		rds_ibdev->pd = NULL;
 		goto put_dev;
 	}
+	rds_ibdev->rid_hdrs_pool = dma_pool_create(device->name,
+						   device->dma_device,
+						   sizeof(struct rds_header),
+						   L1_CACHE_BYTES, 0);
+	if (!rds_ibdev->rid_hdrs_pool)
+		goto put_dev;
 
 	rds_ibdev->mr_1m_pool =
 		rds_ib_create_mr_pool(rds_ibdev, RDS_IB_MR_1M_POOL);
diff --git a/net/rds/ib.h b/net/rds/ib.h
index f2b558e..6e6f247 100644
--- a/net/rds/ib.h
+++ b/net/rds/ib.h
@@ -165,8 +165,8 @@ struct rds_ib_connection {
 	/* tx */
 	struct rds_ib_work_ring	i_send_ring;
 	struct rm_data_op	*i_data_op;
-	struct rds_header	*i_send_hdrs;
-	dma_addr_t		i_send_hdrs_dma;
+	struct rds_header	**i_send_hdrs;
+	dma_addr_t		*i_send_hdrs_dma;
 	struct rds_ib_send_work *i_sends;
 	atomic_t		i_signaled_sends;
 
@@ -175,8 +175,8 @@ struct rds_ib_connection {
 	struct rds_ib_work_ring	i_recv_ring;
 	struct rds_ib_incoming	*i_ibinc;
 	u32			i_recv_data_rem;
-	struct rds_header	*i_recv_hdrs;
-	dma_addr_t		i_recv_hdrs_dma;
+	struct rds_header	**i_recv_hdrs;
+	dma_addr_t		*i_recv_hdrs_dma;
 	struct rds_ib_recv_work *i_recvs;
 	u64			i_ack_recv;	/* last ACK received */
 	struct rds_ib_refill_cache i_cache_incs;
@@ -246,6 +246,7 @@ struct rds_ib_device {
 	struct list_head	conn_list;
 	struct ib_device	*dev;
 	struct ib_pd		*pd;
+	struct dma_pool		*rid_hdrs_pool; /* RDS headers DMA pool */
 	bool                    use_fastreg;
 
 	unsigned int		max_mrs;
@@ -381,7 +382,11 @@ int rds_ib_cm_handle_connect(struct rdma_cm_id *cm_id,
 int rds_ib_cm_initiate_connect(struct rdma_cm_id *cm_id, bool isv6);
 void rds_ib_cm_connect_complete(struct rds_connection *conn,
 				struct rdma_cm_event *event);
-
+struct rds_header **rds_dma_hdrs_alloc(struct ib_device *ibdev,
+				       struct dma_pool *pool,
+				       dma_addr_t **dma_addrs, u32 num_hdrs);
+void rds_dma_hdrs_free(struct dma_pool *pool, struct rds_header **hdrs,
+		       dma_addr_t *dma_addrs, u32 num_hdrs);
 
 #define rds_ib_conn_error(conn, fmt...) \
 	__rds_ib_conn_error(conn, KERN_WARNING "RDS/IB: " fmt)
diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
index 233f136..d08251f 100644
--- a/net/rds/ib_cm.c
+++ b/net/rds/ib_cm.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -439,6 +439,68 @@ static inline void ibdev_put_vector(struct rds_ib_device *rds_ibdev, int index)
 	rds_ibdev->vector_load[index]--;
 }
 
+/* Allocate DMA coherent memory to be used to store struct rds_header for
+ * sending/receiving packets.  The pointers to the DMA memory and the
+ * associated DMA addresses are stored in two arrays.
+ *
+ * @ibdev: the IB device
+ * @pool: the DMA memory pool
+ * @dma_addrs: pointer to the array for storing DMA addresses
+ * @num_hdrs: number of headers to allocate
+ *
+ * It returns the pointer to the array storing the DMA memory pointers.  On
+ * error, NULL pointer is returned.
+ */
+struct rds_header **rds_dma_hdrs_alloc(struct ib_device *ibdev,
+				       struct dma_pool *pool,
+				       dma_addr_t **dma_addrs, u32 num_hdrs)
+{
+	struct rds_header **hdrs;
+	dma_addr_t *hdr_daddrs;
+	u32 i;
+
+	hdrs = kvmalloc_node(sizeof(*hdrs) * num_hdrs, GFP_KERNEL,
+			     ibdev_to_node(ibdev));
+	if (!hdrs)
+		return NULL;
+
+	hdr_daddrs = kvmalloc_node(sizeof(*hdr_daddrs) * num_hdrs, GFP_KERNEL,
+				   ibdev_to_node(ibdev));
+	if (!hdr_daddrs) {
+		kvfree(hdrs);
+		return NULL;
+	}
+
+	for (i = 0; i < num_hdrs; i++) {
+		hdrs[i] = dma_pool_zalloc(pool, GFP_KERNEL, &hdr_daddrs[i]);
+		if (!hdrs[i]) {
+			rds_dma_hdrs_free(pool, hdrs, hdr_daddrs, i);
+			return NULL;
+		}
+	}
+
+	*dma_addrs = hdr_daddrs;
+	return hdrs;
+}
+
+/* Free the DMA memory used to store struct rds_header.
+ *
+ * @pool: the DMA memory pool
+ * @hdrs: pointer to the array storing DMA memory pointers
+ * @dma_addrs: pointer to the array storing DMA addresses
+ * @num_hdars: number of headers to free.
+ */
+void rds_dma_hdrs_free(struct dma_pool *pool, struct rds_header **hdrs,
+		       dma_addr_t *dma_addrs, u32 num_hdrs)
+{
+	u32 i;
+
+	for (i = 0; i < num_hdrs; i++)
+		dma_pool_free(pool, hdrs[i], dma_addrs[i]);
+	kvfree(hdrs);
+	kvfree(dma_addrs);
+}
+
 /*
  * This needs to be very careful to not leave IS_ERR pointers around for
  * cleanup to trip over.
@@ -451,6 +513,7 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 	struct ib_cq_init_attr cq_attr = {};
 	struct rds_ib_device *rds_ibdev;
 	int ret, fr_queue_space;
+	struct dma_pool *pool;
 
 	/*
 	 * It's normal to see a null device if an incoming connection races
@@ -541,31 +604,28 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 		goto recv_cq_out;
 	}
 
-	ic->i_send_hdrs = ib_dma_alloc_coherent(dev,
-					   ic->i_send_ring.w_nr *
-						sizeof(struct rds_header),
-					   &ic->i_send_hdrs_dma, GFP_KERNEL);
+	pool = rds_ibdev->rid_hdrs_pool;
+	ic->i_send_hdrs = rds_dma_hdrs_alloc(dev, pool, &ic->i_send_hdrs_dma,
+					     ic->i_send_ring.w_nr);
 	if (!ic->i_send_hdrs) {
 		ret = -ENOMEM;
-		rdsdebug("ib_dma_alloc_coherent send failed\n");
+		rdsdebug("DMA send hdrs alloc failed\n");
 		goto qp_out;
 	}
 
-	ic->i_recv_hdrs = ib_dma_alloc_coherent(dev,
-					   ic->i_recv_ring.w_nr *
-						sizeof(struct rds_header),
-					   &ic->i_recv_hdrs_dma, GFP_KERNEL);
+	ic->i_recv_hdrs = rds_dma_hdrs_alloc(dev, pool, &ic->i_recv_hdrs_dma,
+					     ic->i_recv_ring.w_nr);
 	if (!ic->i_recv_hdrs) {
 		ret = -ENOMEM;
-		rdsdebug("ib_dma_alloc_coherent recv failed\n");
+		rdsdebug("DMA recv hdrs alloc failed\n");
 		goto send_hdrs_dma_out;
 	}
 
-	ic->i_ack = ib_dma_alloc_coherent(dev, sizeof(struct rds_header),
-				       &ic->i_ack_dma, GFP_KERNEL);
+	ic->i_ack = dma_pool_zalloc(pool, GFP_KERNEL,
+				    &ic->i_ack_dma);
 	if (!ic->i_ack) {
 		ret = -ENOMEM;
-		rdsdebug("ib_dma_alloc_coherent ack failed\n");
+		rdsdebug("DMA ack header alloc failed\n");
 		goto recv_hdrs_dma_out;
 	}
 
@@ -596,17 +656,23 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 
 sends_out:
 	vfree(ic->i_sends);
+
 ack_dma_out:
-	ib_dma_free_coherent(dev, sizeof(struct rds_header),
-			     ic->i_ack, ic->i_ack_dma);
+	dma_pool_free(pool, ic->i_ack, ic->i_ack_dma);
+	ic->i_ack = NULL;
+
 recv_hdrs_dma_out:
-	ib_dma_free_coherent(dev, ic->i_recv_ring.w_nr *
-					sizeof(struct rds_header),
-					ic->i_recv_hdrs, ic->i_recv_hdrs_dma);
+	rds_dma_hdrs_free(pool, ic->i_recv_hdrs, ic->i_recv_hdrs_dma,
+			  ic->i_recv_ring.w_nr);
+	ic->i_recv_hdrs = NULL;
+	ic->i_recv_hdrs_dma = NULL;
+
 send_hdrs_dma_out:
-	ib_dma_free_coherent(dev, ic->i_send_ring.w_nr *
-					sizeof(struct rds_header),
-					ic->i_send_hdrs, ic->i_send_hdrs_dma);
+	rds_dma_hdrs_free(pool, ic->i_send_hdrs, ic->i_send_hdrs_dma,
+			  ic->i_send_ring.w_nr);
+	ic->i_send_hdrs = NULL;
+	ic->i_send_hdrs_dma = NULL;
+
 qp_out:
 	rdma_destroy_qp(ic->i_cm_id);
 recv_cq_out:
@@ -984,8 +1050,6 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
 		 ic->i_cm_id ? ic->i_cm_id->qp : NULL);
 
 	if (ic->i_cm_id) {
-		struct ib_device *dev = ic->i_cm_id->device;
-
 		rdsdebug("disconnecting cm %p\n", ic->i_cm_id);
 		err = rdma_disconnect(ic->i_cm_id);
 		if (err) {
@@ -1035,24 +1099,39 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
 			ib_destroy_cq(ic->i_recv_cq);
 		}
 
-		/* then free the resources that ib callbacks use */
-		if (ic->i_send_hdrs)
-			ib_dma_free_coherent(dev,
-					   ic->i_send_ring.w_nr *
-						sizeof(struct rds_header),
-					   ic->i_send_hdrs,
-					   ic->i_send_hdrs_dma);
-
-		if (ic->i_recv_hdrs)
-			ib_dma_free_coherent(dev,
-					   ic->i_recv_ring.w_nr *
-						sizeof(struct rds_header),
-					   ic->i_recv_hdrs,
-					   ic->i_recv_hdrs_dma);
-
-		if (ic->i_ack)
-			ib_dma_free_coherent(dev, sizeof(struct rds_header),
-					     ic->i_ack, ic->i_ack_dma);
+		if (ic->rds_ibdev) {
+			struct dma_pool *pool;
+
+			pool = ic->rds_ibdev->rid_hdrs_pool;
+
+			/* then free the resources that ib callbacks use */
+			if (ic->i_send_hdrs) {
+				rds_dma_hdrs_free(pool, ic->i_send_hdrs,
+						  ic->i_send_hdrs_dma,
+						  ic->i_send_ring.w_nr);
+				ic->i_send_hdrs = NULL;
+				ic->i_send_hdrs_dma = NULL;
+			}
+
+			if (ic->i_recv_hdrs) {
+				rds_dma_hdrs_free(pool, ic->i_recv_hdrs,
+						  ic->i_recv_hdrs_dma,
+						  ic->i_recv_ring.w_nr);
+				ic->i_recv_hdrs = NULL;
+				ic->i_recv_hdrs_dma = NULL;
+			}
+
+			if (ic->i_ack) {
+				dma_pool_free(pool, ic->i_ack, ic->i_ack_dma);
+				ic->i_ack = NULL;
+			}
+		} else {
+			WARN_ON(ic->i_send_hdrs);
+			WARN_ON(ic->i_send_hdrs_dma);
+			WARN_ON(ic->i_recv_hdrs);
+			WARN_ON(ic->i_recv_hdrs_dma);
+			WARN_ON(ic->i_ack);
+		}
 
 		if (ic->i_sends)
 			rds_ib_send_clear_ring(ic);
@@ -1071,9 +1150,6 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
 		ic->i_pd = NULL;
 		ic->i_send_cq = NULL;
 		ic->i_recv_cq = NULL;
-		ic->i_send_hdrs = NULL;
-		ic->i_recv_hdrs = NULL;
-		ic->i_ack = NULL;
 	}
 	BUG_ON(ic->rds_ibdev);
 
diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index a0f99bb..bcc2a71 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -61,7 +61,7 @@ void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
 		recv->r_wr.num_sge = RDS_IB_RECV_SGE;
 
 		sge = &recv->r_sge[0];
-		sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
+		sge->addr = ic->i_recv_hdrs_dma[i];
 		sge->length = sizeof(struct rds_header);
 		sge->lkey = ic->i_pd->local_dma_lkey;
 
@@ -343,7 +343,7 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn,
 	WARN_ON(ret != 1);
 
 	sge = &recv->r_sge[0];
-	sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
+	sge->addr = ic->i_recv_hdrs_dma[recv - ic->i_recvs];
 	sge->length = sizeof(struct rds_header);
 
 	sge = &recv->r_sge[1];
@@ -861,7 +861,7 @@ static void rds_ib_process_recv(struct rds_connection *conn,
 	}
 	data_len -= sizeof(struct rds_header);
 
-	ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];
+	ihdr = ic->i_recv_hdrs[recv - ic->i_recvs];
 
 	/* Validate the checksum. */
 	if (!rds_message_verify_checksum(ihdr)) {
diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
index dfe6237..58b82d8 100644
--- a/net/rds/ib_send.c
+++ b/net/rds/ib_send.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -201,7 +201,8 @@ void rds_ib_send_init_ring(struct rds_ib_connection *ic)
 		send->s_wr.ex.imm_data = 0;
 
 		sge = &send->s_sge[0];
-		sge->addr = ic->i_send_hdrs_dma + (i * sizeof(struct rds_header));
+		sge->addr = ic->i_send_hdrs_dma[i];
+
 		sge->length = sizeof(struct rds_header);
 		sge->lkey = ic->i_pd->local_dma_lkey;
 
@@ -631,11 +632,13 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 		send->s_queued = jiffies;
 		send->s_op = NULL;
 
-		send->s_sge[0].addr = ic->i_send_hdrs_dma
-			+ (pos * sizeof(struct rds_header));
+		send->s_sge[0].addr = ic->i_send_hdrs_dma[pos];
+
 		send->s_sge[0].length = sizeof(struct rds_header);
 
-		memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));
+		memcpy(ic->i_send_hdrs[pos], &rm->m_inc.i_hdr,
+		       sizeof(struct rds_header));
+
 
 		/* Set up the data, if present */
 		if (i < work_alloc
@@ -674,7 +677,7 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 			 &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
 
 		if (ic->i_flowctl && adv_credits) {
-			struct rds_header *hdr = &ic->i_send_hdrs[pos];
+			struct rds_header *hdr = ic->i_send_hdrs[pos];
 
 			/* add credit and redo the header checksum */
 			hdr->h_credit = adv_credits;
-- 
1.8.3.1

Re: [PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[santosh.shilimkar]

On 9/30/19 2:08 AM, Ka-Cheong Poon wrote:
> Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
> of contiguous DMA coherent memory to store struct rds_header for
> sending/receiving packets.  The memory allocated is then partitioned
> into struct rds_header.  This is not necessary and can be costly at
> times when memory is fragmented.  Instead, RDS should use the DMA
> memory pool interface to handle this.
> 
> Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
> Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
> ---
Thanks for getting this out on the list Ka-Cheong.

Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

Re: [PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[David Miller]

From: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Date: Mon, 30 Sep 2019 02:08:00 -0700

> Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
> of contiguous DMA coherent memory to store struct rds_header for
> sending/receiving packets.  The memory allocated is then partitioned
> into struct rds_header.  This is not necessary and can be costly at
> times when memory is fragmented.  Instead, RDS should use the DMA
> memory pool interface to handle this.
> 
> Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
> Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>

This is trading a one-time overhead for extra levels of dereferencing
on every single descriptor access in the fast paths.

I do not agree with this tradeoff, please implement this more
reasonably.

Re: [PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[Ka-Cheong Poon]

On 10/2/19 1:16 AM, David Miller wrote:
> From: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
> Date: Mon, 30 Sep 2019 02:08:00 -0700
> 
>> Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
>> of contiguous DMA coherent memory to store struct rds_header for
>> sending/receiving packets.  The memory allocated is then partitioned
>> into struct rds_header.  This is not necessary and can be costly at
>> times when memory is fragmented.  Instead, RDS should use the DMA
>> memory pool interface to handle this.
>>
>> Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
>> Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
> 
> This is trading a one-time overhead for extra levels of dereferencing
> on every single descriptor access in the fast paths.
> 
> I do not agree with this tradeoff, please implement this more
> reasonably.


The problem with the existing way of pre-allocation is
that when there are a lot of RDS connections, the call to
ib_dma_alloc_coherent() can fail because there are not
enough contiguous memory pages available.  It is causing
problems in production systems.

And the i_{recv|send|_hdrs_dma array dereferencing is done
at send/receive ring initialization and refill.  It is not
done at every access of the header.

Thanks.


-- 
K. Poon
ka-cheong.poon@oracle.com

Re: [PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[Håkon Bugge]

> On 2 Oct 2019, at 07:20, Ka-Cheong Poon <ka-cheong.poon@oracle.com> wrote:
> 
> On 10/2/19 1:16 AM, David Miller wrote:
>> From: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
>> Date: Mon, 30 Sep 2019 02:08:00 -0700
>>> Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
>>> of contiguous DMA coherent memory to store struct rds_header for
>>> sending/receiving packets.  The memory allocated is then partitioned
>>> into struct rds_header.  This is not necessary and can be costly at
>>> times when memory is fragmented.  Instead, RDS should use the DMA
>>> memory pool interface to handle this.
>>> 
>>> Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
>>> Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
>> This is trading a one-time overhead for extra levels of dereferencing
>> on every single descriptor access in the fast paths.
>> I do not agree with this tradeoff, please implement this more
>> reasonably.
> 
> 
> The problem with the existing way of pre-allocation is
> that when there are a lot of RDS connections, the call to
> ib_dma_alloc_coherent() can fail because there are not
> enough contiguous memory pages available.  It is causing
> problems in production systems.
> 
> And the i_{recv|send|_hdrs_dma array dereferencing is done
> at send/receive ring initialization and refill.  It is not
> done at every access of the header.

The commit removes costly order:4 allocations (with the default 1024 #entries in the recv work-queue). These allocations may need reclaims and/or compaction. At worst, they may fail.

Consider a switch failure, thousands of RDS IB connections, and their corresponding QPs, need to be resurrected. Each QP needs this order:4 allocation, and they are all created in close proximity in time, leading to an immense memory hog.


Thxs, Håkon




> Thanks.
> 
> 
> -- 
> K. Poon
> ka-cheong.poon@oracle.com
> 
> 
> 

Re: [PATCH net-next] net/rds: Use DMA memory pool allocation for rds_header

[David Miller]

From: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Date: Wed, 2 Oct 2019 13:20:22 +0800

> And the i_{recv|send|_hdrs_dma array dereferencing is done
> at send/receive ring initialization and refill.  It is not
> done at every access of the header.

Ok, please add this info to the commit message and resubmit.

Thanks.

[PATCH net-next v2] net/rds: Use DMA memory pool allocation for rds_header

[Ka-Cheong Poon]

Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
of contiguous DMA coherent memory to store struct rds_header for
sending/receiving packets.  The memory allocated is then partitioned
into struct rds_header.  This is not necessary and can be costly at
times when memory is fragmented.  Instead, RDS should use the DMA
memory pool interface to handle this.  The DMA addresses of the pre-
allocated headers are stored in an array.  At send/receive ring
initialization and refill time, this arrary is de-referenced to get
the DMA addresses.  This array is not accessed at send/receive packet
processing.

Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
---
 net/rds/ib.c      |  10 +++-
 net/rds/ib.h      |  15 +++--
 net/rds/ib_cm.c   | 166 +++++++++++++++++++++++++++++++++++++++---------------
 net/rds/ib_recv.c |   8 +--
 net/rds/ib_send.c |  15 +++--
 5 files changed, 153 insertions(+), 61 deletions(-)

diff --git a/net/rds/ib.c b/net/rds/ib.c
index 45acab2..01dc189 100644
--- a/net/rds/ib.c
+++ b/net/rds/ib.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -107,6 +107,8 @@ static void rds_ib_dev_free(struct work_struct *work)
 		rds_ib_destroy_mr_pool(rds_ibdev->mr_1m_pool);
 	if (rds_ibdev->pd)
 		ib_dealloc_pd(rds_ibdev->pd);
+	if (rds_ibdev->rid_hdrs_pool)
+		dma_pool_destroy(rds_ibdev->rid_hdrs_pool);
 
 	list_for_each_entry_safe(i_ipaddr, i_next, &rds_ibdev->ipaddr_list, list) {
 		list_del(&i_ipaddr->list);
@@ -179,6 +181,12 @@ static void rds_ib_add_one(struct ib_device *device)
 		rds_ibdev->pd = NULL;
 		goto put_dev;
 	}
+	rds_ibdev->rid_hdrs_pool = dma_pool_create(device->name,
+						   device->dma_device,
+						   sizeof(struct rds_header),
+						   L1_CACHE_BYTES, 0);
+	if (!rds_ibdev->rid_hdrs_pool)
+		goto put_dev;
 
 	rds_ibdev->mr_1m_pool =
 		rds_ib_create_mr_pool(rds_ibdev, RDS_IB_MR_1M_POOL);
diff --git a/net/rds/ib.h b/net/rds/ib.h
index f2b558e..6e6f247 100644
--- a/net/rds/ib.h
+++ b/net/rds/ib.h
@@ -165,8 +165,8 @@ struct rds_ib_connection {
 	/* tx */
 	struct rds_ib_work_ring	i_send_ring;
 	struct rm_data_op	*i_data_op;
-	struct rds_header	*i_send_hdrs;
-	dma_addr_t		i_send_hdrs_dma;
+	struct rds_header	**i_send_hdrs;
+	dma_addr_t		*i_send_hdrs_dma;
 	struct rds_ib_send_work *i_sends;
 	atomic_t		i_signaled_sends;
 
@@ -175,8 +175,8 @@ struct rds_ib_connection {
 	struct rds_ib_work_ring	i_recv_ring;
 	struct rds_ib_incoming	*i_ibinc;
 	u32			i_recv_data_rem;
-	struct rds_header	*i_recv_hdrs;
-	dma_addr_t		i_recv_hdrs_dma;
+	struct rds_header	**i_recv_hdrs;
+	dma_addr_t		*i_recv_hdrs_dma;
 	struct rds_ib_recv_work *i_recvs;
 	u64			i_ack_recv;	/* last ACK received */
 	struct rds_ib_refill_cache i_cache_incs;
@@ -246,6 +246,7 @@ struct rds_ib_device {
 	struct list_head	conn_list;
 	struct ib_device	*dev;
 	struct ib_pd		*pd;
+	struct dma_pool		*rid_hdrs_pool; /* RDS headers DMA pool */
 	bool                    use_fastreg;
 
 	unsigned int		max_mrs;
@@ -381,7 +382,11 @@ int rds_ib_cm_handle_connect(struct rdma_cm_id *cm_id,
 int rds_ib_cm_initiate_connect(struct rdma_cm_id *cm_id, bool isv6);
 void rds_ib_cm_connect_complete(struct rds_connection *conn,
 				struct rdma_cm_event *event);
-
+struct rds_header **rds_dma_hdrs_alloc(struct ib_device *ibdev,
+				       struct dma_pool *pool,
+				       dma_addr_t **dma_addrs, u32 num_hdrs);
+void rds_dma_hdrs_free(struct dma_pool *pool, struct rds_header **hdrs,
+		       dma_addr_t *dma_addrs, u32 num_hdrs);
 
 #define rds_ib_conn_error(conn, fmt...) \
 	__rds_ib_conn_error(conn, KERN_WARNING "RDS/IB: " fmt)
diff --git a/net/rds/ib_cm.c b/net/rds/ib_cm.c
index 233f136..d08251f 100644
--- a/net/rds/ib_cm.c
+++ b/net/rds/ib_cm.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -439,6 +439,68 @@ static inline void ibdev_put_vector(struct rds_ib_device *rds_ibdev, int index)
 	rds_ibdev->vector_load[index]--;
 }
 
+/* Allocate DMA coherent memory to be used to store struct rds_header for
+ * sending/receiving packets.  The pointers to the DMA memory and the
+ * associated DMA addresses are stored in two arrays.
+ *
+ * @ibdev: the IB device
+ * @pool: the DMA memory pool
+ * @dma_addrs: pointer to the array for storing DMA addresses
+ * @num_hdrs: number of headers to allocate
+ *
+ * It returns the pointer to the array storing the DMA memory pointers.  On
+ * error, NULL pointer is returned.
+ */
+struct rds_header **rds_dma_hdrs_alloc(struct ib_device *ibdev,
+				       struct dma_pool *pool,
+				       dma_addr_t **dma_addrs, u32 num_hdrs)
+{
+	struct rds_header **hdrs;
+	dma_addr_t *hdr_daddrs;
+	u32 i;
+
+	hdrs = kvmalloc_node(sizeof(*hdrs) * num_hdrs, GFP_KERNEL,
+			     ibdev_to_node(ibdev));
+	if (!hdrs)
+		return NULL;
+
+	hdr_daddrs = kvmalloc_node(sizeof(*hdr_daddrs) * num_hdrs, GFP_KERNEL,
+				   ibdev_to_node(ibdev));
+	if (!hdr_daddrs) {
+		kvfree(hdrs);
+		return NULL;
+	}
+
+	for (i = 0; i < num_hdrs; i++) {
+		hdrs[i] = dma_pool_zalloc(pool, GFP_KERNEL, &hdr_daddrs[i]);
+		if (!hdrs[i]) {
+			rds_dma_hdrs_free(pool, hdrs, hdr_daddrs, i);
+			return NULL;
+		}
+	}
+
+	*dma_addrs = hdr_daddrs;
+	return hdrs;
+}
+
+/* Free the DMA memory used to store struct rds_header.
+ *
+ * @pool: the DMA memory pool
+ * @hdrs: pointer to the array storing DMA memory pointers
+ * @dma_addrs: pointer to the array storing DMA addresses
+ * @num_hdars: number of headers to free.
+ */
+void rds_dma_hdrs_free(struct dma_pool *pool, struct rds_header **hdrs,
+		       dma_addr_t *dma_addrs, u32 num_hdrs)
+{
+	u32 i;
+
+	for (i = 0; i < num_hdrs; i++)
+		dma_pool_free(pool, hdrs[i], dma_addrs[i]);
+	kvfree(hdrs);
+	kvfree(dma_addrs);
+}
+
 /*
  * This needs to be very careful to not leave IS_ERR pointers around for
  * cleanup to trip over.
@@ -451,6 +513,7 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 	struct ib_cq_init_attr cq_attr = {};
 	struct rds_ib_device *rds_ibdev;
 	int ret, fr_queue_space;
+	struct dma_pool *pool;
 
 	/*
 	 * It's normal to see a null device if an incoming connection races
@@ -541,31 +604,28 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 		goto recv_cq_out;
 	}
 
-	ic->i_send_hdrs = ib_dma_alloc_coherent(dev,
-					   ic->i_send_ring.w_nr *
-						sizeof(struct rds_header),
-					   &ic->i_send_hdrs_dma, GFP_KERNEL);
+	pool = rds_ibdev->rid_hdrs_pool;
+	ic->i_send_hdrs = rds_dma_hdrs_alloc(dev, pool, &ic->i_send_hdrs_dma,
+					     ic->i_send_ring.w_nr);
 	if (!ic->i_send_hdrs) {
 		ret = -ENOMEM;
-		rdsdebug("ib_dma_alloc_coherent send failed\n");
+		rdsdebug("DMA send hdrs alloc failed\n");
 		goto qp_out;
 	}
 
-	ic->i_recv_hdrs = ib_dma_alloc_coherent(dev,
-					   ic->i_recv_ring.w_nr *
-						sizeof(struct rds_header),
-					   &ic->i_recv_hdrs_dma, GFP_KERNEL);
+	ic->i_recv_hdrs = rds_dma_hdrs_alloc(dev, pool, &ic->i_recv_hdrs_dma,
+					     ic->i_recv_ring.w_nr);
 	if (!ic->i_recv_hdrs) {
 		ret = -ENOMEM;
-		rdsdebug("ib_dma_alloc_coherent recv failed\n");
+		rdsdebug("DMA recv hdrs alloc failed\n");
 		goto send_hdrs_dma_out;
 	}
 
-	ic->i_ack = ib_dma_alloc_coherent(dev, sizeof(struct rds_header),
-				       &ic->i_ack_dma, GFP_KERNEL);
+	ic->i_ack = dma_pool_zalloc(pool, GFP_KERNEL,
+				    &ic->i_ack_dma);
 	if (!ic->i_ack) {
 		ret = -ENOMEM;
-		rdsdebug("ib_dma_alloc_coherent ack failed\n");
+		rdsdebug("DMA ack header alloc failed\n");
 		goto recv_hdrs_dma_out;
 	}
 
@@ -596,17 +656,23 @@ static int rds_ib_setup_qp(struct rds_connection *conn)
 
 sends_out:
 	vfree(ic->i_sends);
+
 ack_dma_out:
-	ib_dma_free_coherent(dev, sizeof(struct rds_header),
-			     ic->i_ack, ic->i_ack_dma);
+	dma_pool_free(pool, ic->i_ack, ic->i_ack_dma);
+	ic->i_ack = NULL;
+
 recv_hdrs_dma_out:
-	ib_dma_free_coherent(dev, ic->i_recv_ring.w_nr *
-					sizeof(struct rds_header),
-					ic->i_recv_hdrs, ic->i_recv_hdrs_dma);
+	rds_dma_hdrs_free(pool, ic->i_recv_hdrs, ic->i_recv_hdrs_dma,
+			  ic->i_recv_ring.w_nr);
+	ic->i_recv_hdrs = NULL;
+	ic->i_recv_hdrs_dma = NULL;
+
 send_hdrs_dma_out:
-	ib_dma_free_coherent(dev, ic->i_send_ring.w_nr *
-					sizeof(struct rds_header),
-					ic->i_send_hdrs, ic->i_send_hdrs_dma);
+	rds_dma_hdrs_free(pool, ic->i_send_hdrs, ic->i_send_hdrs_dma,
+			  ic->i_send_ring.w_nr);
+	ic->i_send_hdrs = NULL;
+	ic->i_send_hdrs_dma = NULL;
+
 qp_out:
 	rdma_destroy_qp(ic->i_cm_id);
 recv_cq_out:
@@ -984,8 +1050,6 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
 		 ic->i_cm_id ? ic->i_cm_id->qp : NULL);
 
 	if (ic->i_cm_id) {
-		struct ib_device *dev = ic->i_cm_id->device;
-
 		rdsdebug("disconnecting cm %p\n", ic->i_cm_id);
 		err = rdma_disconnect(ic->i_cm_id);
 		if (err) {
@@ -1035,24 +1099,39 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
 			ib_destroy_cq(ic->i_recv_cq);
 		}
 
-		/* then free the resources that ib callbacks use */
-		if (ic->i_send_hdrs)
-			ib_dma_free_coherent(dev,
-					   ic->i_send_ring.w_nr *
-						sizeof(struct rds_header),
-					   ic->i_send_hdrs,
-					   ic->i_send_hdrs_dma);
-
-		if (ic->i_recv_hdrs)
-			ib_dma_free_coherent(dev,
-					   ic->i_recv_ring.w_nr *
-						sizeof(struct rds_header),
-					   ic->i_recv_hdrs,
-					   ic->i_recv_hdrs_dma);
-
-		if (ic->i_ack)
-			ib_dma_free_coherent(dev, sizeof(struct rds_header),
-					     ic->i_ack, ic->i_ack_dma);
+		if (ic->rds_ibdev) {
+			struct dma_pool *pool;
+
+			pool = ic->rds_ibdev->rid_hdrs_pool;
+
+			/* then free the resources that ib callbacks use */
+			if (ic->i_send_hdrs) {
+				rds_dma_hdrs_free(pool, ic->i_send_hdrs,
+						  ic->i_send_hdrs_dma,
+						  ic->i_send_ring.w_nr);
+				ic->i_send_hdrs = NULL;
+				ic->i_send_hdrs_dma = NULL;
+			}
+
+			if (ic->i_recv_hdrs) {
+				rds_dma_hdrs_free(pool, ic->i_recv_hdrs,
+						  ic->i_recv_hdrs_dma,
+						  ic->i_recv_ring.w_nr);
+				ic->i_recv_hdrs = NULL;
+				ic->i_recv_hdrs_dma = NULL;
+			}
+
+			if (ic->i_ack) {
+				dma_pool_free(pool, ic->i_ack, ic->i_ack_dma);
+				ic->i_ack = NULL;
+			}
+		} else {
+			WARN_ON(ic->i_send_hdrs);
+			WARN_ON(ic->i_send_hdrs_dma);
+			WARN_ON(ic->i_recv_hdrs);
+			WARN_ON(ic->i_recv_hdrs_dma);
+			WARN_ON(ic->i_ack);
+		}
 
 		if (ic->i_sends)
 			rds_ib_send_clear_ring(ic);
@@ -1071,9 +1150,6 @@ void rds_ib_conn_path_shutdown(struct rds_conn_path *cp)
 		ic->i_pd = NULL;
 		ic->i_send_cq = NULL;
 		ic->i_recv_cq = NULL;
-		ic->i_send_hdrs = NULL;
-		ic->i_recv_hdrs = NULL;
-		ic->i_ack = NULL;
 	}
 	BUG_ON(ic->rds_ibdev);
 
diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index a0f99bb..bcc2a71 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -61,7 +61,7 @@ void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
 		recv->r_wr.num_sge = RDS_IB_RECV_SGE;
 
 		sge = &recv->r_sge[0];
-		sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
+		sge->addr = ic->i_recv_hdrs_dma[i];
 		sge->length = sizeof(struct rds_header);
 		sge->lkey = ic->i_pd->local_dma_lkey;
 
@@ -343,7 +343,7 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn,
 	WARN_ON(ret != 1);
 
 	sge = &recv->r_sge[0];
-	sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
+	sge->addr = ic->i_recv_hdrs_dma[recv - ic->i_recvs];
 	sge->length = sizeof(struct rds_header);
 
 	sge = &recv->r_sge[1];
@@ -861,7 +861,7 @@ static void rds_ib_process_recv(struct rds_connection *conn,
 	}
 	data_len -= sizeof(struct rds_header);
 
-	ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];
+	ihdr = ic->i_recv_hdrs[recv - ic->i_recvs];
 
 	/* Validate the checksum. */
 	if (!rds_message_verify_checksum(ihdr)) {
diff --git a/net/rds/ib_send.c b/net/rds/ib_send.c
index dfe6237..58b82d8 100644
--- a/net/rds/ib_send.c
+++ b/net/rds/ib_send.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006, 2017 Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2019 Oracle and/or its affiliates. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
@@ -201,7 +201,8 @@ void rds_ib_send_init_ring(struct rds_ib_connection *ic)
 		send->s_wr.ex.imm_data = 0;
 
 		sge = &send->s_sge[0];
-		sge->addr = ic->i_send_hdrs_dma + (i * sizeof(struct rds_header));
+		sge->addr = ic->i_send_hdrs_dma[i];
+
 		sge->length = sizeof(struct rds_header);
 		sge->lkey = ic->i_pd->local_dma_lkey;
 
@@ -631,11 +632,13 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 		send->s_queued = jiffies;
 		send->s_op = NULL;
 
-		send->s_sge[0].addr = ic->i_send_hdrs_dma
-			+ (pos * sizeof(struct rds_header));
+		send->s_sge[0].addr = ic->i_send_hdrs_dma[pos];
+
 		send->s_sge[0].length = sizeof(struct rds_header);
 
-		memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));
+		memcpy(ic->i_send_hdrs[pos], &rm->m_inc.i_hdr,
+		       sizeof(struct rds_header));
+
 
 		/* Set up the data, if present */
 		if (i < work_alloc
@@ -674,7 +677,7 @@ int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 			 &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
 
 		if (ic->i_flowctl && adv_credits) {
-			struct rds_header *hdr = &ic->i_send_hdrs[pos];
+			struct rds_header *hdr = ic->i_send_hdrs[pos];
 
 			/* add credit and redo the header checksum */
 			hdr->h_credit = adv_credits;
-- 
1.8.3.1

Re: [PATCH net-next v2] net/rds: Use DMA memory pool allocation for rds_header

[David Miller]

From: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
Date: Wed,  2 Oct 2019 21:11:08 -0700

> Currently, RDS calls ib_dma_alloc_coherent() to allocate a large piece
> of contiguous DMA coherent memory to store struct rds_header for
> sending/receiving packets.  The memory allocated is then partitioned
> into struct rds_header.  This is not necessary and can be costly at
> times when memory is fragmented.  Instead, RDS should use the DMA
> memory pool interface to handle this.  The DMA addresses of the pre-
> allocated headers are stored in an array.  At send/receive ring
> initialization and refill time, this arrary is de-referenced to get
> the DMA addresses.  This array is not accessed at send/receive packet
> processing.
> 
> Suggested-by: Håkon Bugge <haakon.bugge@oracle.com>
> Signed-off-by: Ka-Cheong Poon <ka-cheong.poon@oracle.com>
> Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>

Applied.