From: David Miller <davem@davemloft.net>
From: Christoph Lameter <clameter@sgi.com>
To: clameter@sgi.com
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, ak@suse.de,
mathieu.desnoyers@polymtl.ca
Subject: Re: Some interesting observations when trying to optimize vmstat handling
Date: Thu, 08 Nov 2007 15:24:08 -0800 (PST) [thread overview]
Date: Thu, 8 Nov 2007 11:58:58 -0800 (PST) [thread overview]
Message-ID: <20071108.152408.157342087.davem@davemloft.net> (raw)
In-Reply-To: <Pine.LNX.4.64.0711081141180.9694@schroedinger.engr.sgi.com>
> The problem with cmpxchg_local here is that the differential has to
> be read before we execute the cmpxchg_local. So the cacheline is
> acquired first in read mode and then made exclusive on executing the
> cmpxchg_local.
I bet this can be defeated by prefetching for a write before
the read, but of course this won't help if the read is
being used to conditionally avoid the cmpxchg_local but I don't
think that's what you're trying to do here.
I've always wanted to add a write prefetch at the beginning of all of
the sparc64 atomic operation primitives because of this problem.
I just never got around to measuring if it's worthwhile or not.
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prev parent reply other threads:[~2007-11-08 23:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-08 19:58 Christoph Lameter
2007-11-08 23:07 ` Andi Kleen
2007-11-08 23:25 ` Christoph Lameter
2007-11-09 0:19 ` Jeremy Fitzhardinge
2007-11-09 15:56 ` Andi Kleen
2007-11-08 23:24 ` David Miller, Christoph Lameter [this message]
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