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[209.85.220.65]) by mx.google.com with SMTPS id f7sor68381969pfb.22.2019.08.06.04.07.47 for (Google Transport Security); Tue, 06 Aug 2019 04:07:47 -0700 (PDT) Received-SPF: pass (google.com: domain of minchan.kim@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=FKiohG4p; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=tBmS1JSg6R7dIdS7tcKHXNzn/jUBrwmVmbb/LUzYkA4=; b=FKiohG4pWZeA/Wi7DBC/9npqkDrHpyRoEZz0rJr3UUucKs69b2m0OSmC0nKoqoEBW7 5a5fisl81W7ayWltjhWVDhYcauX5oI8qjT4HtPAD8MYvTTn2BUR7Z+/ra9jmsBm5ygxl coLvx5hCepcasDv3Ne7A33Zn9x+18/WPTkwpxyTWKXEQavMv1FfQZWEk9n3vFCWxJKBz 8xgjqJToD3aUbClZjNybApCSYfWR+J9s7Cr5z2gCs2zn7kfaA/XDfENps51XKzcC7h+v MMuNw3N9Qr5VXXVcVPES+JzklSH8uO3a+z/VBP70OotlcR+ykPpu1CCL5PGcPfSbf/4h l5DA== X-Google-Smtp-Source: APXvYqyN06dee+YCHt2A2RzCyf1hHdHxVyVKw3mol+ZH/H3Wfu7dAX7tuJm7I+hqEodTVg3369khvw== X-Received: by 2002:a62:3895:: with SMTP id f143mr3075201pfa.116.1565089667635; Tue, 06 Aug 2019 04:07:47 -0700 (PDT) Received: from google.com ([2401:fa00:d:0:98f1:8b3d:1f37:3e8]) by smtp.gmail.com with ESMTPSA id h129sm82492287pfb.110.2019.08.06.04.07.39 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 06 Aug 2019 04:07:46 -0700 (PDT) Date: Tue, 6 Aug 2019 20:07:37 +0900 From: Minchan Kim To: Michal Hocko Cc: Joel Fernandes , linux-kernel@vger.kernel.org, Robin Murphy , Alexey Dobriyan , Andrew Morton , Borislav Petkov , Brendan Gregg , Catalin Marinas , Christian Hansen , dancol@google.com, fmayer@google.com, "H. Peter Anvin" , Ingo Molnar , Jonathan Corbet , Kees Cook , kernel-team@android.com, linux-api@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Mike Rapoport , namhyung@google.com, paulmck@linux.ibm.com, Roman Gushchin , Stephen Rothwell , surenb@google.com, Thomas Gleixner , tkjos@google.com, Vladimir Davydov , Vlastimil Babka , Will Deacon Subject: Re: [PATCH v4 3/5] [RFC] arm64: Add support for idle bit in swap PTE Message-ID: <20190806110737.GB32615@google.com> References: <20190805170451.26009-1-joel@joelfernandes.org> <20190805170451.26009-3-joel@joelfernandes.org> <20190806084203.GJ11812@dhcp22.suse.cz> <20190806103627.GA218260@google.com> <20190806104755.GR11812@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190806104755.GR11812@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) 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, Aug 06, 2019 at 12:47:55PM +0200, Michal Hocko wrote: > On Tue 06-08-19 06:36:27, Joel Fernandes wrote: > > On Tue, Aug 06, 2019 at 10:42:03AM +0200, Michal Hocko wrote: > > > On Mon 05-08-19 13:04:49, Joel Fernandes (Google) wrote: > > > > This bit will be used by idle page tracking code to correctly identify > > > > if a page that was swapped out was idle before it got swapped out. > > > > Without this PTE bit, we lose information about if a page is idle or not > > > > since the page frame gets unmapped. > > > > > > And why do we need that? Why cannot we simply assume all swapped out > > > pages to be idle? They were certainly idle enough to be reclaimed, > > > right? Or what does idle actualy mean here? > > > > Yes, but other than swapping, in Android a page can be forced to be swapped > > out as well using the new hints that Minchan is adding? > > Yes and that is effectivelly making them idle, no? 1. mark page-A idle which was present at that time. 2. run workload 3. page-A is touched several times 4. *sudden* memory pressure happen so finally page A is finally swapped out 5. now see the page A idle - but it's incorrect.