From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753383AbdLHVCZ (ORCPT ); Fri, 8 Dec 2017 16:02:25 -0500 Received: from mail-it0-f67.google.com ([209.85.214.67]:35596 "EHLO mail-it0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750980AbdLHVCX (ORCPT ); Fri, 8 Dec 2017 16:02:23 -0500 X-Google-Smtp-Source: AGs4zMaWNWtB4D5azzvujSvnQ6XkUL2EN1RscbbR43kKPNMw6VN+KqTdzQXhxphSjSeVdSAkNDzoSw== Date: Fri, 8 Dec 2017 13:02:20 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com 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 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> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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