From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 717166B0038 for ; Fri, 8 Dec 2017 16:02:24 -0500 (EST) Received: by mail-io0-f198.google.com with SMTP id r140so251937iod.12 for ; Fri, 08 Dec 2017 13:02:24 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id n129sor1471246itb.101.2017.12.08.13.02.23 for (Google Transport Security); Fri, 08 Dec 2017 13:02:23 -0800 (PST) Date: Fri, 8 Dec 2017 13:02:20 -0800 (PST) From: David Rientjes Subject: Re: [PATCH v2] mm: terminate shrink_slab loop if signal is pending In-Reply-To: <20171208012305.83134-1-surenb@google.com> Message-ID: References: <20171208012305.83134-1-surenb@google.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, mhocko@suse.com, hannes@cmpxchg.org, hillf.zj@alibaba-inc.com, minchan@kernel.org, mgorman@techsingularity.net, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, timmurray@google.com, tkjos@google.com 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 > > --- > 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@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org