From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=0.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A669C31E40 for ; Tue, 6 Aug 2019 14:48:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D9795214C6 for ; Tue, 6 Aug 2019 14:48:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565102887; bh=lJu1d00IddRtlJ3PKabQL9ziweXPEZv093P9dtW0kDk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ZY8Y1+qPA6I3ITxQhfmqwoJtehf8AB32AmzVyGQiCZ7Gdhk1NbhARKWjPucpXXK2c OufRSDta3d1jb1xyGDKjeJoGHR0YeSBIUlWW09JWaKNHhzEpHUkfPZVNQ6pByLstz5 JlMtYrko0g969rq0FVFEHy9uJip1XvT/ANl5zOGs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733114AbfHFOsC (ORCPT ); Tue, 6 Aug 2019 10:48:02 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:36166 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730289AbfHFOsC (ORCPT ); Tue, 6 Aug 2019 10:48:02 -0400 Received: by mail-pf1-f195.google.com with SMTP id r7so41637354pfl.3; Tue, 06 Aug 2019 07:48:01 -0700 (PDT) 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=hPKj1q9pzAw01F3LuwbWC2NJPbuIQVTFZWSZ1tXqf8g=; b=QJ2Cxb8mgxyBmBWFhf+Q6WKHeahBHKbgCHhSNQaP7XebbA7RxANJ+gPXMpYWZCcMSu X359Nf5xHy+rw4UZX4hMjsVID68kwhu4AqXw7NM/rCH4HqG+ZDOo5A5SAswJAMLlEJK8 z7yFfZyf/V+gepSBrVsmRbdzILbhwZtR1o1W4fb6SKsWY3NHkX3qpRxDA2HxO6BGES9y 7Qu4NWlphGVXGI6g6CukvGsD2JQ+Nz4GEb7FiYPGqmYJMTe0BmSKOTXNkgyOg7WD/Aw6 4M1QqWSg1xq7Cal5OUE8Rp+Rt9jVJd04zrvUG6ifgzm+idylAD6YNxfXOLHqgvOdlUn2 Iq4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=hPKj1q9pzAw01F3LuwbWC2NJPbuIQVTFZWSZ1tXqf8g=; b=K2WMk6WWHTsTERuVMC7kv09GFMyYcLFY5BFUux7z2uUr+3hePWprl6pTKaMS43E8pJ ogsDWQDYiqD3zZXRaX7ZFfgCo0oEJyDscfGCY0Kepo8DXPLwNs36mXtEuueakAiBVBoM cNlvF0eyNoWzaytsGpuFeVvbGZkg3eduqTM1lzkzXu81y6LwvU0HI12nfCUhCXVWvcsB 3p+zcRgzFQ7goSarzAljD0hqd7rfIbutlyiBstrTBgT+o4q1Cv8bhABYH22nGwPQIHpx 9AZXNMPqPxu+qdUi8tlxIu95JXT5uzcBifJLYpmlCyUIfp7r1BTkJfvWOEk472v2kbjV QIfg== X-Gm-Message-State: APjAAAXxuWRtNTSa56bSFuCeVozeLzLyADpieyh5ZLYehgyIaaHPEPLt ubfk6YfNfeBEayMyBCDhXfc= X-Google-Smtp-Source: APXvYqykjh8W3ip+qMmEJ9I/374nqTdJG5EsvPbtew94zlKNiZ7NYnx4nG7TA1fgWOgH43oAutyB7w== X-Received: by 2002:a63:1b56:: with SMTP id b22mr3320797pgm.265.1565102881165; Tue, 06 Aug 2019 07:48:01 -0700 (PDT) Received: from google.com ([122.38.223.241]) by smtp.gmail.com with ESMTPSA id r12sm72175100pgb.73.2019.08.06.07.47.50 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 06 Aug 2019 07:47:59 -0700 (PDT) Date: Tue, 6 Aug 2019 23:47:47 +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: <20190806144747.GA72938@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> <20190806111446.GA117316@google.com> <20190806115703.GY11812@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190806115703.GY11812@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Aug 06, 2019 at 01:57:03PM +0200, Michal Hocko wrote: > On Tue 06-08-19 07:14:46, Joel Fernandes wrote: > > 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? > > > > That depends on how you think of it. > > I would much prefer to have it documented so that I do not have to guess ;) > > > If you are thinking of a monitoring > > process like a heap profiler, then from the heap profiler's (that only cares > > about the process it is monitoring) perspective it will look extremely odd if > > pages that are recently accessed by the process appear to be idle which would > > falsely look like those processes are leaking memory. The reality being, > > Android forced those pages into swap because of other reasons. I would like > > for the swapping mechanism, whether forced swapping or memory reclaim, not to > > interfere with the idle detection. > > Hmm, but how are you going to handle situation when the page is unmapped > and refaulted again (e.g. a normal reclaim of a pagecache)? You are > losing that information same was as in the swapout case, no? Or am I > missing something? If page is unmapped, it's not a idle memory any longer because it's free memory. We could detect the pte is not present. If page is refaulted, it's not a idle memory any longer because it's accessed again. We could detect it because the newly allocated page doesn't have a PG_idle page flag. Both case, idle page tracking couldn't report them as IDLE so it's okay.