Messages in this thread | | | Date | Tue, 09 Jun 2009 14:56:15 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH 3/4] Count the number of times zone_reclaim() scans and fails |
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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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