On 2018/09/06 20:35, Michal Hocko wrote: > On Sat 01-09-18 20:48:57, Tetsuo Handa wrote: >> On 2018/08/07 5:51, Michal Hocko wrote: >>>> At the risk of continually repeating the same statement, the oom reaper >>>> cannot provide the direct feedback for all possible memory freeing. >>>> Waking up periodically and finding mm->mmap_sem contended is one problem, >>>> but the other problem that I've already shown is the unnecessary oom >>>> killing of additional processes while a thread has already reached >>>> exit_mmap(). The oom reaper cannot free page tables which is problematic >>>> for malloc implementations such as tcmalloc that do not release virtual >>>> memory. >>> >>> But once we know that the exit path is past the point of blocking we can >>> have MMF_OOM_SKIP handover from the oom_reaper to the exit path. So the >>> oom_reaper doesn't hide the current victim too early and we can safely >>> wait for the exit path to reclaim the rest. So there is a feedback >>> channel. I would even do not mind to poll for that state few times - >>> similar to polling for the mmap_sem. But it would still be some feedback >>> rather than a certain amount of time has passed since the last check. >> >> Michal, will you show us how we can handover as an actual patch? I'm not >> happy with postponing current situation with just your wish to handover. > > I am sorry but I am bussy with other higher priority issues. I believe I > have outlined the scheme that might work (see above). All it takes is to > look into that closer a play with it. If you are too busy, please show "the point of no-blocking" using source code instead. If such "the point of no-blocking" really exists, it can be executed by allocating threads. I think that such "the point of no-blocking" is so late stage of freeing that it makes no difference with timeout based back off.
