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u+In2SWCPRnQBHp+wGtMtzqrKAYjcRfWNA5bvoQwUIgAOs/Frxh50NBlKSiiukdb87Eupz5/Zo1aNhqy0Xits50ztLVO/x0lhIFDZVCaleXo+nBNWlZAvKOr/fon42ehcdw8xG+CaexjAQwNohzukCqRM1GKN5aWjHtjLfFP7iYvZbhYizFM8uR6g0bdjhOvCNkOQ7CjMY8qunop/rRbdYMCDRy5Zn/SfP/5IHQaWExish2UYIS7/UiU2C0j8oy+j3sAU6rO/VCM05oPwwX/sJltJ+2imhd1du5AF/1ij/eTj+UZ/BehaoebxYzoKTnFek/MD X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 16 Aug 2023, Huang, Ying wrote: > Michal Hocko 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.