From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com [209.85.214.182]) by kanga.kvack.org (Postfix) with ESMTP id 6BDF26B0038 for ; Sat, 28 Nov 2015 11:10:30 -0500 (EST) Received: by obdgf3 with SMTP id gf3so100853179obd.3 for ; Sat, 28 Nov 2015 08:10:30 -0800 (PST) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [2001:e42:101:1:202:181:97:72]) by mx.google.com with ESMTPS id vw13si565710oeb.82.2015.11.28.08.10.28 for (version=TLS1 cipher=AES128-SHA bits=128/128); Sat, 28 Nov 2015 08:10:29 -0800 (PST) Subject: Re: [RFC PATCH -v2] mm, oom: introduce oom reaper From: Tetsuo Handa References: <1448467018-20603-1-git-send-email-mhocko@kernel.org> <1448640772-30147-1-git-send-email-mhocko@kernel.org> <201511281339.JHH78172.SLOQFOFHVFOMJt@I-love.SAKURA.ne.jp> In-Reply-To: <201511281339.JHH78172.SLOQFOFHVFOMJt@I-love.SAKURA.ne.jp> Message-Id: <201511290110.FJB87096.OHJLVQOSFFtMFO@I-love.SAKURA.ne.jp> Date: Sun, 29 Nov 2015 01:10:10 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org, linux-mm@kvack.org Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, mgorman@suse.de, rientjes@google.com, riel@redhat.com, hughd@google.com, oleg@redhat.com, andrea@kernel.org, linux-kernel@vger.kernel.org, mhocko@suse.com Tetsuo Handa wrote: > > Users of mmap_sem which need it for write should be carefully reviewed > > to use _killable waiting as much as possible and reduce allocations > > requests done with the lock held to absolute minimum to reduce the risk > > even further. > > It will be nice if we can have down_write_killable()/down_read_killable(). It will be nice if we can also have __GFP_KILLABLE. Although currently it can't be perfect because reclaim functions called from __alloc_pages_slowpath() use unkillable waits, starting from just bail out as with __GFP_NORETRY when fatal_signal_pending(current) is true will be helpful. So far I'm hitting no problem with testers except the one using mmap()/munmap(). I think that cmpxchg() was not needed. diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c2ab7f9..1a65739 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -483,8 +483,6 @@ static int oom_reaper(void *unused) static void wake_oom_reaper(struct mm_struct *mm) { - struct mm_struct *old_mm; - if (!oom_reaper_th) return; @@ -492,14 +490,15 @@ static void wake_oom_reaper(struct mm_struct *mm) * Make sure that only a single mm is ever queued for the reaper * because multiple are not necessary and the operation might be * disruptive so better reduce it to the bare minimum. + * Caller is serialized by oom_lock mutex. */ - old_mm = cmpxchg(&mm_to_reap, NULL, mm); - if (!old_mm) { + if (!mm_to_reap) { /* * Pin the given mm. Use mm_count instead of mm_users because * we do not want to delay the address space tear down. */ atomic_inc(&mm->mm_count); + mm_to_reap = mm; wake_up(&oom_reaper_wait); } } -- 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