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Subject: Re: [PATCH 1/8] drivers/random: Cache align ip_random better
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Matt Mackall <mpm@selenic.com>
Cc: Hugh Dickins <hughd@google.com>, George Spelvin <linux@horizon.com>,
        penberg@cs.helsinki.fi, herbert@gondor.hengli.com.au,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
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Date: Wed, 16 Mar 2011 20:26:33 +0100
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> I think this alignment exists to minimize the number of cacheline
> bounces on SMP as this can be a pretty hot structure in the network
> stack. It could probably benefit from a per-cpu treatment.
> 

Well, this is a mostly read area of memory, dirtied every 5 minutes.

Compare this to 'jiffies' for example ;)

What could be done is to embed 'ip_cnt' inside ip_keydata[0] for
example, to avoid wasting a cache line for one bit ;)


c1606c40 b ip_cnt
<hole>
c1606c80 b ip_keydata


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