linux-kernel - Re: [PATCH 00/25] Cleanup and optimise the page allocator V5

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Message-ID: <alpine.DEB.1.10.0903201059240.3740@qirst.com>
Date:	Fri, 20 Mar 2009 11:00:42 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Linux Memory Management List <linux-mm@...ck.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 00/25] Cleanup and optimise the page allocator V5

On Fri, 20 Mar 2009, Mel Gorman wrote:

> The lock contention on some machines goes up for the the zone->lru_lock
> and zone->lock locks which can regress some workloads even though others on
> the same machine still go faster. For netperf, a lock called slock-AF_INET
> seemed very important although I didn't look too closely other than noting
> contention went up. The zone->lock gets hammered a lot by high order allocs
> and frees coming from SLUB which are not covered by the PCP allocator in
> this patchset. zone->lru_lock goes up is less clear but as it's page cache
> releases but overall contention may be up because CPUs are spending less
> time with interrupts disabled and more time trying to do real work but
> contending on the locks.

We can tune SLUB to buffer more pages if the lru lock becomes too hot.


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