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* [PATCH net] net: pktgen: fix pkt_size
@ 2016-09-29 14:04 Paolo Abeni
  2016-09-29 17:11 ` Sergei Shtylyov
  0 siblings, 1 reply; 2+ messages in thread
From: Paolo Abeni @ 2016-09-29 14:04 UTC (permalink / raw)
  To: netdev; +Cc: David S. Miller, Bogdan Hamciuc, Ben Greear

The commit 879c7220e828 ("net: pktgen: Observe needed_headroom
of the device") increased the 'pkt_overhead' field value by
LL_RESERVED_SPACE.
As a side effect the generated packet size, computed as:

	/* Eth + IPh + UDPh + mpls */
	datalen = pkt_dev->cur_pkt_size - 14 - 20 - 8 -
		  pkt_dev->pkt_overhead;

is decreased by the same value.
The above changed slightly the behavior of existing pktgen users,
and made the interface somewhat inconsistent.
Fix it by restoring the previous pkt_overhead value and using
LL_RESERVED_SPACE as extralen in skb allocation.
Also, change pktgen_alloc_skb() to only partially reserve
the headroom to allow the caller to prefetch from ll header
start.

Fixes: 879c7220e828 ("net: pktgen: Observe needed_headroom of the device")
Suggested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/core/pktgen.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index bbd118b..5c9b397 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -2286,7 +2286,7 @@ out:
 
 static inline void set_pkt_overhead(struct pktgen_dev *pkt_dev)
 {
-	pkt_dev->pkt_overhead = LL_RESERVED_SPACE(pkt_dev->odev);
+	pkt_dev->pkt_overhead = 0;
 	pkt_dev->pkt_overhead += pkt_dev->nr_labels*sizeof(u32);
 	pkt_dev->pkt_overhead += VLAN_TAG_SIZE(pkt_dev);
 	pkt_dev->pkt_overhead += SVLAN_TAG_SIZE(pkt_dev);
@@ -2777,13 +2777,13 @@ static void pktgen_finalize_skb(struct pktgen_dev *pkt_dev, struct sk_buff *skb,
 }
 
 static struct sk_buff *pktgen_alloc_skb(struct net_device *dev,
-					struct pktgen_dev *pkt_dev,
-					unsigned int extralen)
+					struct pktgen_dev *pkt_dev)
 {
+	unsigned int extralen = LL_RESERVED_SPACE(dev);
 	struct sk_buff *skb = NULL;
-	unsigned int size = pkt_dev->cur_pkt_size + 64 + extralen +
-			    pkt_dev->pkt_overhead;
+	unsigned int size;
 
+	size = pkt_dev->cur_pkt_size + 64 + extralen + pkt_dev->pkt_overhead;
 	if (pkt_dev->flags & F_NODE) {
 		int node = pkt_dev->node >= 0 ? pkt_dev->node : numa_node_id();
 
@@ -2796,8 +2796,9 @@ static struct sk_buff *pktgen_alloc_skb(struct net_device *dev,
 		 skb = __netdev_alloc_skb(dev, size, GFP_NOWAIT);
 	}
 
+	/* the caller prefetch from skb->data and reserve for the mac hdr */
 	if (likely(skb))
-		skb_reserve(skb, LL_RESERVED_SPACE(dev));
+		skb_reserve(skb, extralen - 16);
 
 	return skb;
 }
@@ -2830,16 +2831,14 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev,
 	mod_cur_headers(pkt_dev);
 	queue_map = pkt_dev->cur_queue_map;
 
-	datalen = (odev->hard_header_len + 16) & ~0xf;
-
-	skb = pktgen_alloc_skb(odev, pkt_dev, datalen);
+	skb = pktgen_alloc_skb(odev, pkt_dev);
 	if (!skb) {
 		sprintf(pkt_dev->result, "No memory");
 		return NULL;
 	}
 
 	prefetchw(skb->data);
-	skb_reserve(skb, datalen);
+	skb_reserve(skb, 16);
 
 	/*  Reserve for ethernet and IP header  */
 	eth = (__u8 *) skb_push(skb, 14);
@@ -2959,7 +2958,7 @@ static struct sk_buff *fill_packet_ipv6(struct net_device *odev,
 	mod_cur_headers(pkt_dev);
 	queue_map = pkt_dev->cur_queue_map;
 
-	skb = pktgen_alloc_skb(odev, pkt_dev, 16);
+	skb = pktgen_alloc_skb(odev, pkt_dev);
 	if (!skb) {
 		sprintf(pkt_dev->result, "No memory");
 		return NULL;
-- 
1.8.3.1

^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH net] net: pktgen: fix pkt_size
  2016-09-29 14:04 [PATCH net] net: pktgen: fix pkt_size Paolo Abeni
@ 2016-09-29 17:11 ` Sergei Shtylyov
  0 siblings, 0 replies; 2+ messages in thread
From: Sergei Shtylyov @ 2016-09-29 17:11 UTC (permalink / raw)
  To: Paolo Abeni, netdev; +Cc: David S. Miller, Bogdan Hamciuc, Ben Greear

Hello.

On 09/29/2016 05:04 PM, Paolo Abeni wrote:

> The commit 879c7220e828 ("net: pktgen: Observe needed_headroom
> of the device") increased the 'pkt_overhead' field value by
> LL_RESERVED_SPACE.
> As a side effect the generated packet size, computed as:
>
> 	/* Eth + IPh + UDPh + mpls */
> 	datalen = pkt_dev->cur_pkt_size - 14 - 20 - 8 -
> 		  pkt_dev->pkt_overhead;
>
> is decreased by the same value.
> The above changed slightly the behavior of existing pktgen users,
> and made the interface somewhat inconsistent.
> Fix it by restoring the previous pkt_overhead value and using
> LL_RESERVED_SPACE as extralen in skb allocation.
> Also, change pktgen_alloc_skb() to only partially reserve
> the headroom to allow the caller to prefetch from ll header
> start.
>
> Fixes: 879c7220e828 ("net: pktgen: Observe needed_headroom of the device")
> Suggested-by: Ben Greear <greearb@candelatech.com>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
>  net/core/pktgen.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> index bbd118b..5c9b397 100644
> --- a/net/core/pktgen.c
> +++ b/net/core/pktgen.c
[...]
> @@ -2796,8 +2796,9 @@ static struct sk_buff *pktgen_alloc_skb(struct net_device *dev,
>  		 skb = __netdev_alloc_skb(dev, size, GFP_NOWAIT);
>  	}
>
> +	/* the caller prefetch from skb->data and reserve for the mac hdr */

    Pre-fetches and reserves?

[...]

MBR, Sergei

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2016-09-29 14:04 [PATCH net] net: pktgen: fix pkt_size Paolo Abeni
2016-09-29 17:11 ` Sergei Shtylyov

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