Messages in this thread | | | Date | Wed, 16 Aug 2023 13:23:00 -0700 (PDT) | From | "Lameter, Christopher" <> | Subject | Re: [PATCH] mm: fix draining remote pageset |
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On Wed, 16 Aug 2023, Huang, Ying wrote:
> Michal Hocko <mhocko@suse.com> writes: >>>> Why is that a problem? >>> >>> The pages of the remote zone may be kept in the local per-CPU pageset >>> for long time as long as there's no page allocation/freeing on the >>> logical CPU. In addition to the logical CPU goes idle, this is also >>> possible if the logical CPU is busy in the user space. >> >> But why is this a problem? Is the scale of the problem sufficient to >> trigger out of memory situations or be otherwise harmful? > > This may trigger premature page reclaiming. The pages in the PCP of the > remote zone would have been freed to satisfy the page allocation for the > remote zone to avoid page reclaiming. It's highly possible that the > local CPU just allocate/free from/to the remote zone temporarily. So, > we should free PCP pages of the remote zone if there is no page > allocation/freeing from/to the remote zone for 3 seconds. > > This will not trigger OOM, because all PCP will be drained if allocation > failed after direct reclaiming.
I think this is a minor issue but its cleaner behavior. vmstat refresh's should continue as long as there are pages queued in remote pcps.
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