From: Matt Mackall <mpm@selenic.com>
To: Eric Dumazet <eric.dumazet@gmail.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
Subject: Re: [PATCH 1/8] drivers/random: Cache align ip_random better
Date: Wed, 16 Mar 2011 14:55:07 -0500 [thread overview]
Message-ID: <1300305307.3128.528.camel@calx> (raw)
In-Reply-To: <1300303593.3202.30.camel@edumazet-laptop>
On Wed, 2011-03-16 at 20:26 +0100, Eric Dumazet wrote:
> > 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
Yeah. I actually think we're due for rethinking this entire process. It
dates back to when we introduced syncookies in the 90s and it shows. The
fact that we've started abusing it for other things doesn't help.
--
Mathematics is the supreme nostalgia of our time.
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prev parent reply other threads:[~2011-03-16 19:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-14 0:20 [PATCH 1/8] drivers/random: Cache align ip_random better George Spelvin
2011-03-16 2:54 ` Matt Mackall
2011-03-16 6:24 ` Pekka Enberg
2011-03-16 17:17 ` Hugh Dickins
2011-03-16 18:10 ` George Spelvin
2011-03-16 18:42 ` Hugh Dickins
2011-03-16 19:45 ` George Spelvin
2011-03-22 9:03 ` Herbert Xu
2011-03-16 18:23 ` Matt Mackall
2011-03-16 19:26 ` Eric Dumazet
2011-03-16 19:55 ` Matt Mackall [this message]
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