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. > Signed-off-by: Suren Baghdasaryan <sur...@google.com> > > --- > 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
