From: Christoph Lameter <cl@linux.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>, Shaohua Li <shaohua.li@intel.com>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
David Rientjes <rientjes@google.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low
Date: Fri, 29 Oct 2010 14:33:02 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1010291425360.26312@router.home> (raw)
In-Reply-To: <20101029112541.8ab906bb.akpm@linux-foundation.org>
On Fri, 29 Oct 2010, Andrew Morton wrote:
> > Doing that caused cache misses in the past and reduced the performance of
> > the ZVCs. This way the threshold is in the same cacheline as the
> > differentials.
>
> This sounds wrong. As long as that threshold isn't stored in a
> cacheline which other CPUs are modifying, all CPUs should be able to
> happily cache it. Maybe it needed a bit of padding inside the zone
> struct.
High speed cpu caches are a very scarce resource. The differentials are
not in the zone struct. Tried to put it onto a single cacheline. Even that
did not do the trick for the large configurations.
The same optimizations are done in the slab allocators by the way.
Use of the percpu_counter() would at least quadruple the cache footprint
in use for the counters. percpu_counters() is using s32 and not s8.
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next prev parent reply other threads:[~2010-10-29 19:33 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-28 15:13 [PATCH 0/2] Reduce the amount of time spent in watermark-related functions V4 Mel Gorman
2010-10-28 15:13 ` [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low Mel Gorman
2010-10-28 22:04 ` Andrew Morton
2010-10-29 10:12 ` Mel Gorman
2010-10-29 19:40 ` Andrew Morton
2010-11-02 0:53 ` Shaohua Li
2010-11-09 11:33 ` Mel Gorman
2010-11-09 16:48 ` Christoph Lameter
2010-10-29 14:58 ` Christoph Lameter
2010-10-29 18:25 ` Andrew Morton
2010-10-29 19:33 ` Christoph Lameter [this message]
2010-10-28 15:13 ` [PATCH 2/2] mm: vmstat: Use a single setter function and callback for adjusting percpu thresholds Mel Gorman
2010-10-28 22:09 ` Andrew Morton
2010-10-29 10:17 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2010-10-27 8:47 [PATCH 0/2] Reduce the amount of time spent in watermark-related functions Mel Gorman
2010-10-27 8:47 ` [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low Mel Gorman
2010-10-27 20:16 ` Christoph Lameter
2010-10-28 1:09 ` KAMEZAWA Hiroyuki
2010-10-28 9:49 ` Mel Gorman
2010-10-28 9:58 ` KAMEZAWA Hiroyuki
2010-11-01 7:06 ` KOSAKI Motohiro
2010-11-26 16:06 ` Kyle McMartin
2010-11-29 9:56 ` Mel Gorman
2010-11-29 13:16 ` Kyle McMartin
2010-11-29 15:08 ` Mel Gorman
2010-11-29 15:22 ` Kyle McMartin
2010-11-29 15:26 ` Kyle McMartin
2010-11-29 15:58 ` Mel Gorman
2010-12-23 22:18 ` David Rientjes
2010-12-23 22:35 ` Andrew Morton
2010-12-23 23:00 ` Kyle McMartin
2010-12-23 23:07 ` David Rientjes
2010-12-23 23:17 ` Andrew Morton
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