On Tue, 21 Aug 2018, Michal Hocko wrote: > > Ok, so it appears you're suggesting a per-mm counter of oom reaper retries > > and once it reaches a certain threshold, either give up and set > > MMF_OOM_SKIP or declare that exit_mmap() is responsible for it. That's > > fine, but obviously I'll be suggesting that the threshold is rather large. > > So if I adjust my patch to be a retry counter rather than timestamp, do > > you have any other reservations? > > It absolutely has to be an internal thing without any user API to be > set. Also I still haven't heard any specific argument why would oom > reaper need to do per-task attempt and loop over all victims on the > list. Maybe you have some examples though. > It would be per-mm in this case, the task itself is no longer important other than printing to the kernel log. I think we could simply print that the oom reaper has reaped mm->owner. The oom reaper would need to loop over the per-mm list because the retry counter is going to have a high threshold so that processes have the ability to free their memory before the oom reaper declares it can no longer make forward progress. We cannot stall trying to reap a single mm with a high retry threshold from a memcg hierarchy when another memcg hierarchy is also oom. The ability for one victim to make forward progress can depend on a lock held by another oom memcg hierarchy where reaping would allow it to be dropped.
