From: Eric Dumazet <eric.dumazet@gmail.com>
To: Shawn Bohrer <sbohrer@rgmadvisors.com>
Cc: netdev@vger.kernel.org
Subject: Re: Increased multicast packet drops in 3.4
Date: Thu, 06 Sep 2012 15:31:57 +0200 [thread overview]
Message-ID: <1346938317.2484.40.camel@edumazet-glaptop> (raw)
In-Reply-To: <1346937667.2484.33.camel@edumazet-glaptop>
On Thu, 2012-09-06 at 15:21 +0200, Eric Dumazet wrote:
>
> Are you receiving fragmented UDP frames ?
>
> I ask this because with latest kernels (linux-3.5), we should no longer
> build a list of skb, but a single skb with page fragments.
>
> commit 3cc4949269e01f39443d0fcfffb5bc6b47878d45
> Author: Eric Dumazet <edumazet@google.com>
> Date: Sat May 19 03:02:20 2012 +0000
>
> ipv4: use skb coalescing in defragmentation
>
> ip_frag_reasm() can use skb_try_coalesce() to build optimized skb,
> reducing memory used by them (truesize), and reducing number of cache
> line misses and overhead for the consumer.
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Alexander Duyck <alexander.h.duyck@intel.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
>
>
Unfortunately mlx4 pulls too many bytes from the frame to skb->head, so
it defeats coalescing completely.
Try following patch (if you also try linux-3.5)
diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index 9d27e42..700e70e 100644
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -150,7 +150,7 @@ enum {
#define ETH_LLC_SNAP_SIZE 8
#define SMALL_PACKET_SIZE (256 - NET_IP_ALIGN)
-#define HEADER_COPY_SIZE (128 - NET_IP_ALIGN)
+#define HEADER_COPY_SIZE ETH_HLEN
#define MLX4_LOOPBACK_TEST_PAYLOAD (HEADER_COPY_SIZE - ETH_HLEN)
#define MLX4_EN_MIN_MTU 46
next prev parent reply other threads:[~2012-09-06 13:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-06 0:11 Increased multicast packet drops in 3.4 Shawn Bohrer
2012-09-06 6:07 ` Eric Dumazet
2012-09-06 6:22 ` Eric Dumazet
2012-09-06 13:03 ` Shawn Bohrer
2012-09-06 13:21 ` Eric Dumazet
2012-09-06 13:31 ` Eric Dumazet [this message]
2012-09-07 4:00 ` Shawn Bohrer
2012-09-07 6:08 ` Eric Dumazet
2012-09-07 22:38 ` Shawn Bohrer
2012-09-06 6:26 ` Eric Dumazet
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