On Sat 23-11-19 13:52:57, Yafang Shao wrote: > On Fri, Nov 22, 2019 at 6:28 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > On Wed 20-11-19 20:23:54, Yafang Shao wrote: > > > On Wed, Nov 20, 2019 at 7:40 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > > > > > On Wed 20-11-19 18:53:44, Yafang Shao wrote: > > > > > On Wed, Nov 20, 2019 at 6:22 PM Michal Hocko <mhocko@xxxxxxxxxx> wrote: > > > > > > > > > > > > On Wed 20-11-19 03:53:05, Yafang Shao wrote: > > > > > > > A task running in a memcg may OOM because of the memory.min settings of his > > > > > > > slibing and parent. If this happens, the current oom messages can't show > > > > > > > why file page cache can't be reclaimed. > > > > > > > > > > > > min limit is not the only way to protect memory from being reclaim. The > > > > > > memory might be pinned or unreclaimable for other reasons (e.g. swap > > > > > > quota exceeded for memcg). > > > > > > > > > > Both swap or unreclaimabed (unevicteable) is printed in OOM messages. > > > > > > > > Not really. Consider a memcg which has reached it's swap limit. The > > > > anonymous memory is not really reclaimable even when there is a lot of > > > > swap space available. > > > > > > > > > > The memcg swap limit is already printed in oom messages, see bellow, > > > > > > [ 141.721625] memory: usage 1228800kB, limit 1228800kB, failcnt 18337 > > > [ 141.721958] swap: usage 0kB, limit 9007199254740988kB, failcnt 0 > > > > But you do not have any insight on the swap limit down the oom > > hierarchy, do you? > > > > > > > Why not just print the memcgs which are under memory.min protection or > > > > > something like a total number of min protected memory ? > > > > > > > > Yes, this would likely help. But the main question really reamains, is > > > > this really worth it? > > > > > > > > > > If it doesn't cost too much, I think it is worth to do it. > > > As the oom path is not the critical path, so adding some print info > > > should not add much overhead. > > > > Generating a lot of output for the oom reports has been a real problem > > in many deployments. > > So why not only print non-zero counters ? > If some counters are 0, we don't print them, that can reduce the oom reports. > > Something like "isolated_file:0 unevictable:0 dirty:0 writeback:0 > unstable:0" can all be removed, > and we consider them as zero by default. because that would make parsing more complex. > I mean we can optimze the OOM reports and only print the useful > information to make it not be a problem in many deployments. We can, but it would be great to have it backed by som real usecase to change the current behavior. I haven't heard anything so far. It is all about "this would be nice" without a strong justification. -- Michal Hocko SUSE Labs
