Re: [PATCH v5 1/2] mm/memcontrol.c: try harder to decrease [memory,memsw].limit_in_bytes

Andrey Ryabinin
2018-01-25T19:44:16Z

On 01/19/2018 04:25 PM, Andrey Ryabinin wrote:
> mem_cgroup_resize_[memsw]_limit() tries to free only 32 (SWAP_CLUSTER_MAX)
> pages on each iteration. This makes it practically impossible to decrease
> limit of memory cgroup. Tasks could easily allocate back 32 pages, so we
> can't reduce memory usage, and once retry_count reaches zero we return
> -EBUSY.
>
> Easy to reproduce the problem by running the following commands:
>
> mkdir /sys/fs/cgroup/memory/test
> echo $$ >> /sys/fs/cgroup/memory/test/tasks
> cat big_file > /dev/null &
> sleep 1 && echo $((100*1024*1024)) > /sys/fs/cgroup/memory/test/memory.limit_in_bytes
> -bash: echo: write error: Device or resource busy
>
> Instead of relying on retry_count, keep retrying the reclaim until the
> desired limit is reached or fail if the reclaim doesn't make any progress
> or a signal is pending.
>
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Shakeel Butt <shakeelb@google.com>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>

Andrew, are you ok to pick up the patch?