netdev - Re: [PATCH 04/10] net: pad skb data and shinfo as a whole rather than individually

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Message-ID: <1334070090.5300.59.camel@edumazet-glaptop>
Date:	Tue, 10 Apr 2012 17:01:30 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ian Campbell <ian.campbell@...rix.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Wei Liu <wei.liu2@...rix.com>, xen-devel@...ts.xen.org
Subject: Re: [PATCH 04/10] net: pad skb data and shinfo as a whole rather
 than individually

On Tue, 2012-04-10 at 15:26 +0100, Ian Campbell wrote:
> This reduces the minimum overhead required for this allocation such that the
> shinfo can be grown in the following patch without overflowing 2048 bytes for a
> 1500 byte frame.
> 
> Reducing this overhead while also growing the shinfo means that sometimes the
> tail end of the data can end up in the same cache line as the beginning of the
> shinfo. Specifically in the case of the 64 byte cache lines on a 64 bit system
> the first 8 bytes of shinfo can overlap the tail cacheline of the data. In many
> cases the allocation slop means that there is no overlap.
> 
> Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> ---

Acked-by: Eric Dumazet <eric.dumazet@...il.com>



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