On Fri, Dec 8, 2017 at 1:02 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Thu, 7 Dec 2017, Suren Baghdasaryan wrote: > >> Slab shrinkers can be quite time consuming and when signal >> is pending they can delay handling of the signal. If fatal >> signal is pending there is no point in shrinking that process >> since it will be killed anyway. This change checks for pending >> fatal signals inside shrink_slab loop and if one is detected >> terminates this loop early. >> > > I've proposed a similar patch in the past, but for a check on TIF_MEMDIE, > which would today be a tsk_is_oom_victim(current), since we had observed > lengthy stalls in reclaim that would have been prevented if the oom victim > had exited out, returned back to the page allocator, allocated with > ALLOC_NO_WATERMARKS, and proceeded to quickly exit. > > I'm not sure that all fatal_signal_pending() tasks should get the same > treatment, but I understand the point that the task is killed and should > free memory when it fully exits. How much memory is unknown. > Thanks for the input. For my particular use case TIF_MEMDIE check would not help because I'm trying to kill a process before OOM kicks in, however the approach is interesting and provides food for thought. > > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> >> >> --- >> V2: >> Sergey Senozhatsky: >> - Fix missing parentheses >> --- >> mm/vmscan.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index c02c850ea349..28e4bdc72c16 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -486,6 +486,13 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, >> .memcg = memcg, >> }; >> >> + /* >> + * We are about to die and free our memory. >> + * Stop shrinking which might delay signal handling. >> + */ >> + if (unlikely(fatal_signal_pending(current))) >> + break; >> + >> /* >> * If kernel memory accounting is disabled, we ignore >> * SHRINKER_MEMCG_AWARE flag and call all shrinkers -- 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>
