linux-kernel - Re: [PATCH] e1000: save skb counts in TX to avoid cache misses

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Date:	Thu, 07 Jun 2012 14:38:17 -0700
From:	Jeff Kirsher <tarbal@...il.com>
To:	Roman Kagan <rkagan@...allels.com>
CC:	stable@...r.kernel.org, Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>,
	Alex Duyck <alexander.h.duyck@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	Dean Nelson <dnelson@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] e1000: save skb counts in TX to avoid cache misses

On 06/07/2012 05:49 AM, Roman Kagan wrote:
> [Upstream commit 31c15a2f24ebdab14333d9bf5df49757842ae2ec with paths
> adjusted to compensate for the drivers/net/ethernet/intel reorg in
> dee1ad47f2ee75f5146d83ca757c1b7861c34c3b]
>
> Author: Dean Nelson <dnelson@...hat.com>
> Date:   Thu Aug 25 14:39:24 2011 +0000
>
>     e1000: save skb counts in TX to avoid cache misses
>
>     Virtual Machines with emulated e1000 network adapter running on Parallels'
>     server were seeing kernel panics due to the e1000 driver dereferencing an
>     unexpected NULL pointer retrieved from buffer_info->skb.
>
>     The problem has been addressed for the e1000e driver, but not for the e1000.
>     Since the two drivers share similar code in the affected area, a port of the
>     following e1000e driver commit solves the issue for the e1000 driver:
>
>     commit 9ed318d546a29d7a591dbe648fd1a2efe3be1180
>     Author: Tom Herbert <therbert@...gle.com>
>     Date:   Wed May 5 14:02:27 2010 +0000
>
>         e1000e: save skb counts in TX to avoid cache misses
>
>         In e1000_tx_map, precompute number of segements and bytecounts which
>         are derived from fields in skb; these are stored in buffer_info.  When
>         cleaning tx in e1000_clean_tx_irq use the values in the associated
>         buffer_info for statistics counting, this eliminates cache misses
>         on skb fields.
>
>     Signed-off-by: Dean Nelson <dnelson@...hat.com>
>     Acked-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
>     Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Roman Kagan <rkagan@...allels.com>
> ---
>  drivers/net/e1000/e1000.h      |    2 ++
>  drivers/net/e1000/e1000_main.c |   18 +++++++++---------
>  2 files changed, 11 insertions(+), 9 deletions(-)
Thanks! I have applied the patch to my queue


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