On Wed, 10 Jan 2018 15:43:17 +0300 Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> wrote: > mem_cgroup_resize_[memsw]_limit() tries to free only 32 (SWAP_CLUSTER_MAX) > pages on each iteration. This makes 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. > Is there any situation under which that mem_cgroup_resize_limit() can get stuck semi-indefinitely in a livelockish state? It isn't very obvious that we're protected from this, so perhaps it would help to have a comment which describes how loop termination is assured? -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
