From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Christoph Lameter <cl@linux-foundation.org>,
yanmin.zhang@intel.com, Wu Fengguang <fengguang.wu@intel.com>,
linuxram@us.ibm.com, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] Count the number of times zone_reclaim() scans and fails
Date: Tue, 09 Jun 2009 14:56:15 -0400 [thread overview]
Message-ID: <4A2EB04F.2090906@redhat.com> (raw)
In-Reply-To: <1244566904-31470-4-git-send-email-mel@csn.ul.ie>
Mel Gorman wrote:
> On NUMA machines, the administrator can configure zone_reclaim_mode that
> is a more targetted form of direct reclaim. On machines with large NUMA
> distances for example, a zone_reclaim_mode defaults to 1 meaning that clean
> unmapped pages will be reclaimed if the zone watermarks are not being met.
>
> There is a heuristic that determines if the scan is worthwhile but it is
> possible that the heuristic will fail and the CPU gets tied up scanning
> uselessly. Detecting the situation requires some guesswork and experimentation
> so this patch adds a counter "zreclaim_failed" to /proc/vmstat. If during
> high CPU utilisation this counter is increasing rapidly, then the resolution
> to the problem may be to set /proc/sys/vm/zone_reclaim_mode to 0.
>
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Rik van Riel <riel@redhat.com>
--
All rights reversed.
WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Christoph Lameter <cl@linux-foundation.org>,
yanmin.zhang@intel.com, Wu Fengguang <fengguang.wu@intel.com>,
linuxram@us.ibm.com, linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] Count the number of times zone_reclaim() scans and fails
Date: Tue, 09 Jun 2009 14:56:15 -0400 [thread overview]
Message-ID: <4A2EB04F.2090906@redhat.com> (raw)
In-Reply-To: <1244566904-31470-4-git-send-email-mel@csn.ul.ie>
Mel Gorman wrote:
> On NUMA machines, the administrator can configure zone_reclaim_mode that
> is a more targetted form of direct reclaim. On machines with large NUMA
> distances for example, a zone_reclaim_mode defaults to 1 meaning that clean
> unmapped pages will be reclaimed if the zone watermarks are not being met.
>
> There is a heuristic that determines if the scan is worthwhile but it is
> possible that the heuristic will fail and the CPU gets tied up scanning
> uselessly. Detecting the situation requires some guesswork and experimentation
> so this patch adds a counter "zreclaim_failed" to /proc/vmstat. If during
> high CPU utilisation this counter is increasing rapidly, then the resolution
> to the problem may be to set /proc/sys/vm/zone_reclaim_mode to 0.
>
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Rik van Riel <riel@redhat.com>
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All rights reversed.
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next prev parent reply other threads:[~2009-06-09 18:56 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-09 17:01 [PATCH 0/4] [RFC] Functional fix to zone_reclaim() and bring behaviour more in line with expectations V2 Mel Gorman
2009-06-09 17:01 ` Mel Gorman
2009-06-09 17:01 ` [PATCH 1/4] Properly account for the number of page cache pages zone_reclaim() can reclaim Mel Gorman
2009-06-09 17:01 ` Mel Gorman
2009-06-09 18:15 ` Rik van Riel
2009-06-09 18:15 ` Rik van Riel
2009-06-10 1:19 ` Wu Fengguang
2009-06-10 1:19 ` Wu Fengguang
2009-06-10 7:31 ` KOSAKI Motohiro
2009-06-10 7:31 ` KOSAKI Motohiro
2009-06-10 10:31 ` Mel Gorman
2009-06-10 10:31 ` Mel Gorman
2009-06-10 11:59 ` Wu Fengguang
2009-06-10 11:59 ` Wu Fengguang
2009-06-10 13:41 ` Mel Gorman
2009-06-10 13:41 ` Mel Gorman
2009-06-10 22:42 ` Ram Pai
2009-06-10 22:42 ` Ram Pai
2009-06-11 13:52 ` Mel Gorman
2009-06-11 13:52 ` Mel Gorman
2009-06-11 1:29 ` Wu Fengguang
2009-06-11 1:29 ` Wu Fengguang
2009-06-11 3:26 ` KOSAKI Motohiro
2009-06-11 3:26 ` KOSAKI Motohiro
2009-06-09 17:01 ` [PATCH 2/4] Do not unconditionally treat zones that fail zone_reclaim() as full Mel Gorman
2009-06-09 17:01 ` Mel Gorman
2009-06-09 18:11 ` Rik van Riel
2009-06-09 18:11 ` Rik van Riel
2009-06-10 1:52 ` KOSAKI Motohiro
2009-06-10 1:52 ` KOSAKI Motohiro
2009-06-09 17:01 ` [PATCH 3/4] Count the number of times zone_reclaim() scans and fails Mel Gorman
2009-06-09 17:01 ` Mel Gorman
2009-06-09 18:56 ` Rik van Riel [this message]
2009-06-09 18:56 ` Rik van Riel
2009-06-10 1:47 ` KOSAKI Motohiro
2009-06-10 1:47 ` KOSAKI Motohiro
2009-06-10 10:36 ` Mel Gorman
2009-06-10 10:36 ` Mel Gorman
2009-06-10 2:10 ` Wu Fengguang
2009-06-10 2:10 ` Wu Fengguang
2009-06-10 10:40 ` Mel Gorman
2009-06-10 10:40 ` Mel Gorman
2009-06-09 17:01 ` [PATCH 4/4] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA Mel Gorman
2009-06-09 17:01 ` Mel Gorman
2009-06-10 1:53 ` KOSAKI Motohiro
2009-06-10 1:53 ` KOSAKI Motohiro
2009-06-10 5:54 ` Andrew Morton
2009-06-10 5:54 ` Andrew Morton
2009-06-10 10:48 ` Mel Gorman
2009-06-10 10:48 ` Mel Gorman
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