linux-kernel - Re: [PATCH 1/8] drivers/random: Cache align ip

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Message-ID: <1300303593.3202.30.camel@edumazet-laptop>
Date:	Wed, 16 Mar 2011 20:26:33 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Matt Mackall <mpm@...enic.com>
Cc:	Hugh Dickins <hughd@...gle.com>,
	George Spelvin <linux@...izon.com>, penberg@...helsinki.fi,
	herbert@...dor.hengli.com.au, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] drivers/random: Cache align ip_random better


> 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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