Tetsuo Handa wrote: > Michal Hocko wrote: > > OK, that would suggest that the oom rework patches are not really > > related. They just moved from the livelock to a sleep which is good in > > general IMHO. We even know that it is most probably the IO that is the > > problem because we know that more than half of the reclaimable memory is > > either dirty or under writeback. That is where you should be looking. > > Why the IO is not making progress or such a slow progress. > > > > A footnote. Regarding this reproducer, the problem was "anybody can declare > OOM and call out_of_memory(). But out_of_memory() does nothing because there > is a thread which has TIF_MEMDIE." before the OOM detection rework patches, > and the problem is "nobody can declare OOM and call out_of_memory(). Although > out_of_memory() will do nothing because there is a thread which has > TIF_MEMDIE." after the OOM detection rework patches. According to kmallocwd, allocating tasks are very slowly able to call out_of_memory() ( http://I-love.SAKURA.ne.jp/tmp/serial-20160313.txt.xz ). It seems that the oom detection rework patches are not really related. > > Dave Chinner wrote at http://lkml.kernel.org/r/20160211225929.GU14668@dastard : > > > Although there are memory allocating tasks passing gfp flags with > > > __GFP_KSWAPD_RECLAIM, kswapd is unable to make forward progress because > > > it is blocked at down() called from memory reclaim path. And since it is > > > legal to block kswapd from memory reclaim path (am I correct?), I think > > > we must not assume that current_is_kswapd() check will break the infinite > > > loop condition. > > > > Right, the threads that are blocked in writeback waiting on memory > > reclaim will be using GFP_NOFS to prevent recursion deadlocks, but > > that does not avoid the problem that kswapd can then get stuck > > on those locks, too. Hence there is no guarantee that kswapd can > > make reclaim progress if it does dirty page writeback... > > Unless we address the issue Dave commented, the OOM detection rework patches > add a new location of livelock (which is demonstrated by this reproducer) in > the memory allocator. It is an unfortunate change that we add a new location > of livelock when we are trying to solve thrashing problem. > The oom detection rework patches did not add a new location of livelock. They just did not address the problem that I/O cannot make progress. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>