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[209.85.220.65]) by mx.google.com with SMTPS id v5sor6533868ioe.13.2019.06.11.05.25.17 for (Google Transport Security); Tue, 11 Jun 2019 05:25:17 -0700 (PDT) Received-SPF: pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=AOEMKo6Q; spf=pass (google.com: domain of laoar.shao@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=laoar.shao@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Gq9CRd934/jSE4tc4Cy61VEetGc4bMbhcoAUH9wfjmA=; b=AOEMKo6QupDfoibyB4JDtla+OGVyHX+uZgoNzqLSKc24MwE2lsliSJhMg8PRNqESaX 7kWkB1yg6tR/mppSsW1SMt08NWvRix0xVWcgS/nxAm8qEmxDTagEmG0gQgFRMB8cHCCR oq9G6AEQ9zjyXqeTRYb93Uyka+jdz+TCmscHhubT1ZxtP61M0SZWYWf2mV+FPicJSTV8 kpERADiNqR3SD2e9gxMa9fimczW/Od5exGRGdR6iJi8gljtz6XU8c+O9KhUr6/fdtc+1 pHbE9YcRCiERLl2oheR8DyUTv4IjqvJHSzFGAJvfAgTPr1Pfcpy2XfomkBqyBoGOEaTU 7uYg== X-Google-Smtp-Source: APXvYqzjRg84fLgMD3IEc7Ck88dUNwnDYn6PxBDGvSm78jme0lIJnzjQ1xVGoygVFyNdi7KCwTGj+1fKFgJ+OLTQCwU= X-Received: by 2002:a6b:8dcf:: with SMTP id p198mr2542052iod.46.1560255917485; Tue, 11 Jun 2019 05:25:17 -0700 (PDT) MIME-Version: 1.0 References: <1560156147-12314-1-git-send-email-laoar.shao@gmail.com> <20190610141242.382cfefa2c98b618d12057fb@linux-foundation.org> In-Reply-To: <20190610141242.382cfefa2c98b618d12057fb@linux-foundation.org> From: Yafang Shao Date: Tue, 11 Jun 2019 20:24:41 +0800 Message-ID: Subject: Re: [PATCH] mm/vmscan: call vmpressure_prio() in kswapd reclaim path To: Andrew Morton Cc: Michal Hocko , Linux MM , shaoyafang@didiglobal.com Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jun 11, 2019 at 5:12 AM Andrew Morton wrote: > > On Mon, 10 Jun 2019 16:42:27 +0800 Yafang Shao wrote: > > > Once the reclaim scanning depth goes too deep, it always mean we are > > under memory pressure now. > > This behavior should be captured by vmpressure_prio(), which should run > > every time when the vmscan's reclaiming priority (scanning depth) > > changes. > > It's possible the scanning depth goes deep in kswapd reclaim path, > > so vmpressure_prio() should be called in this path. > > > > Signed-off-by: Yafang Shao > > What effect does this change have upon userspace? > > Presumably you observed some behaviour(?) and that behaviour was > undesirable(?) and the patch changed that behaviour to something > else(?) and this new behaviour is better for some reason(?). > When there're few free memory, the usespace can receive the critical memory pressure event earlier, because when we try to do direct reclaim we always wakeup the kswapd first. Currently the vmpressure work (vmpressure_work_fn) can only be scheduled in direct reclaim path, and with this change, the vmpressure work can be scheduled in kswapd reclaim path. I think receiving the critical memory pressure event earlier can give the userspace more chance to do something to prevent random OOM. With this change, the vmpressure work will be scheduled more frequent than before when the system is under memory pressure. Thanks Yafang