netdev - Re: [v2 PATCH 1/4] tcp: Fix truesize accounting in tcp_try

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Message-Id: <20120503.042159.938231117013356970.davem@davemloft.net>
Date:	Thu, 03 May 2012 04:21:59 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	alexander.h.duyck@...el.com, netdev@...r.kernel.org,
	jeffrey.t.kirsher@...el.com, edumazet@...gle.com
Subject: Re: [v2 PATCH 1/4] tcp: Fix truesize accounting in tcp_try_coalesce

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 03 May 2012 09:48:54 +0200

> On Thu, 2012-05-03 at 00:18 -0700, Alexander Duyck wrote:
>> This patch addresses several issues in the way we were tracking the
>> truesize in tcp_try_coalesce.
>> 
>> First it was using ksize which prevents us from having a 0 sized head frag
>> and getting a usable result.  To resolve that this patch uses the end
>> pointer which is set based off either ksize, or the frag_size supplied in
>> build_skb.  This allows us to compute the original truesize of the entire
>> buffer and remove that value leaving us with just what was added as pages.
>> 
>> The second issue was the use of skb->len if there is a mergeable head frag.
>> We should only need to remove the size of an data aligned sk_buff from our
>> current skb->truesize to compute the delta for a buffer with a reused head.
>> By using skb->len the value of truesize was being artificially reduced
>> which means that head frags could use more memory than buffers using
>> standard allocations.
>> 
>> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
 ...
> Acked-by: Eric Dumazet <edumazet@...gle.com>

Applied.
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