From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id BF6016B029C for ; Mon, 28 Dec 2015 09:13:49 -0500 (EST) Received: by mail-pa0-f45.google.com with SMTP id cy9so110696410pac.0 for ; Mon, 28 Dec 2015 06:13:49 -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 qn16si2567430pab.207.2015.12.28.06.13.48 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 28 Dec 2015 06:13:48 -0800 (PST) Subject: Re: [PATCH 0/3] OOM detection rework v4 From: Tetsuo Handa References: <1450203586-10959-1-git-send-email-mhocko@kernel.org> <201512242141.EAH69761.MOVFQtHSFOJFLO@I-love.SAKURA.ne.jp> <201512282108.EDI82328.OHFLtVJOSQFMFO@I-love.SAKURA.ne.jp> In-Reply-To: <201512282108.EDI82328.OHFLtVJOSQFMFO@I-love.SAKURA.ne.jp> Message-Id: <201512282313.DHE87075.OSLJOFOtMVQHFF@I-love.SAKURA.ne.jp> Date: Mon, 28 Dec 2015 23:13:31 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: mhocko@kernel.org, akpm@linux-foundation.org Cc: torvalds@linux-foundation.org, hannes@cmpxchg.org, mgorman@suse.de, rientjes@google.com, hillf.zj@alibaba-inc.com, kamezawa.hiroyu@jp.fujitsu.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Tetsuo Handa wrote: > Tetsuo Handa wrote: > > I got OOM killers while running heavy disk I/O (extracting kernel source, > > running lxr's genxref command). (Environ: 4 CPUs / 2048MB RAM / no swap / XFS) > > Do you think these OOM killers reasonable? Too weak against fragmentation? > > Since I cannot establish workload that caused December 24's natural OOM > killers, I used the following stressor for generating similar situation. > I came to feel that I am observing a different problem which is currently hidden behind the "too small to fail" memory-allocation rule. That is, tasks requesting order > 0 pages are continuously losing the competition when tasks requesting order = 0 pages dominate, for reclaimed pages are stolen by tasks requesting order = 0 pages before reclaimed pages are combined to order > 0 pages (or maybe order > 0 pages are immediately split into order = 0 pages due to tasks requesting order = 0 pages). Currently, order <= PAGE_ALLOC_COSTLY_ORDER allocations implicitly retry unless chosen by the OOM killer. Therefore, even if tasks requesting order = 2 pages lost the competition when there are tasks requesting order = 0 pages, the order = 2 allocation request is implicitly retried and therefore the OOM killer is not invoked (though there is a problem that tasks requesting order > 0 allocation will stall as long as tasks requesting order = 0 pages dominate). But this patchset introduced a limit of 16 retries. Thus, if tasks requesting order = 2 pages lost the competition for 16 times due to tasks requesting order = 0 pages, tasks requesting order = 2 pages invoke the OOM killer. To avoid the OOM killer, we need to make sure that pages reclaimed for order > 0 allocations will not be stolen by tasks requesting order = 0 allocations. Is my feeling plausible? -- 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