Messages in this thread | | | Date | Mon, 31 Jan 2022 14:01:18 -0500 | Subject | Re: [PATCH v2 3/3] mm/page_owner: Dump memcg information | From | Waiman Long <> |
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On 1/31/22 04:38, Michal Hocko wrote: > On Sat 29-01-22 15:53:15, Waiman Long wrote: >> It was found that a number of offlined memcgs were not freed because >> they were pinned by some charged pages that were present. Even "echo >> 1 > /proc/sys/vm/drop_caches" wasn't able to free those pages. These >> offlined but not freed memcgs tend to increase in number over time with >> the side effect that percpu memory consumption as shown in /proc/meminfo >> also increases over time. >> >> In order to find out more information about those pages that pin >> offlined memcgs, the page_owner feature is extended to dump memory >> cgroup information especially whether the cgroup is offlined or not. > It is not really clear to me how this is supposed to be used. Are you > really dumping all the pages in the system to find out offline memcgs? > That looks rather clumsy to me. I am not against adding memcg > information to the page owner output. That can be useful in other > contexts.
I am just piggybacking on top of the existing page_owner tool to provide information for me to find out what pages are pinning the dead memcgs. page_owner is a debugging tool that is not turned on by default. We do have to add a kernel parameter and rebooting the system to use that, but that is pretty easy to do once we have a reproducer to reproduce the problem.
Cheers, Longman
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