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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.