From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: Re: [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index Date: Mon, 12 Aug 2019 10:56:20 -0400 Message-ID: <20190812145620.GB224541@google.com> References: <20190807171559.182301-1-joel@joelfernandes.org> <20190807130402.49c9ea8bf144d2f83bfeb353@linux-foundation.org> <20190807204530.GB90900@google.com> <20190807135840.92b852e980a9593fe91fbf59@linux-foundation.org> <20190807213105.GA14622@google.com> <20190808080044.GA18351@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190808080044.GA18351@dhcp22.suse.cz> Sender: linux-kernel-owner@vger.kernel.org To: Michal Hocko Cc: Andrew Morton , linux-kernel@vger.kernel.org, Alexey Dobriyan , 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 , minchan@kernel.org, namhyung@google.com, paulmck@linux.ibm.com, Robin Murphy , Roman Gushchin , Stephen Rothwell List-Id: linux-api@vger.kernel.org On Thu, Aug 08, 2019 at 10:00:44AM +0200, Michal Hocko wrote: > On Wed 07-08-19 17:31:05, Joel Fernandes wrote: > > On Wed, Aug 07, 2019 at 01:58:40PM -0700, Andrew Morton wrote: > > > On Wed, 7 Aug 2019 16:45:30 -0400 Joel Fernandes wrote: > > > > > > > On Wed, Aug 07, 2019 at 01:04:02PM -0700, Andrew Morton wrote: > > > > > On Wed, 7 Aug 2019 13:15:54 -0400 "Joel Fernandes (Google)" wrote: > > > > > > > > > > > In Android, we are using this for the heap profiler (heapprofd) which > > > > > > profiles and pin points code paths which allocates and leaves memory > > > > > > idle for long periods of time. This method solves the security issue > > > > > > with userspace learning the PFN, and while at it is also shown to yield > > > > > > better results than the pagemap lookup, the theory being that the window > > > > > > where the address space can change is reduced by eliminating the > > > > > > intermediate pagemap look up stage. In virtual address indexing, the > > > > > > process's mmap_sem is held for the duration of the access. > > > > > > > > > > So is heapprofd a developer-only thing? Is heapprofd included in > > > > > end-user android loads? If not then, again, wouldn't it be better to > > > > > make the feature Kconfigurable so that Android developers can enable it > > > > > during development then disable it for production kernels? > > > > > > > > Almost all of this code is already configurable with > > > > CONFIG_IDLE_PAGE_TRACKING. If you disable it, then all of this code gets > > > > disabled. > > > > > > > > Or are you referring to something else that needs to be made configurable? > > > > > > Yes - the 300+ lines of code which this patchset adds! > > > > > > The impacted people will be those who use the existing > > > idle-page-tracking feature but who will not use the new feature. I > > > guess we can assume this set is small... > > > > Yes, I think this set should be small. The code size increase of page_idle.o > > is from ~1KB to ~2KB. Most of the extra space is consumed by > > page_idle_proc_generic() function which this patch adds. I don't think adding > > another CONFIG option to disable this while keeping existing > > CONFIG_IDLE_PAGE_TRACKING enabled, is worthwhile but I am open to the > > addition of such an option if anyone feels strongly about it. I believe that > > once this patch is merged, most like this new interface being added is what > > will be used more than the old interface (for some of the usecases) so it > > makes sense to keep it alive with CONFIG_IDLE_PAGE_TRACKING. > > I would tend to agree with Joel here. The functionality falls into an > existing IDLE_PAGE_TRACKING config option quite nicely. If there really > are users who want to save some space and this is standing in the way > then they can easily add a new config option with some justification so > the savings are clear. Without that an additional config simply adds to > the already existing configurability complexity and balkanization. Michal, Andrew, Minchan, Would you have any other review comments on the v5 series? This is just a new interface that does not disrupt existing users of the older page-idle tracking, so as such it is a safe change (as in, doesn't change existing functionality except for the draining bug fix). thanks, - Joel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id D847F7D90F for ; Mon, 12 Aug 2019 14:56:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726791AbfHLO4Y (ORCPT ); Mon, 12 Aug 2019 10:56:24 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:42397 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726786AbfHLO4X (ORCPT ); Mon, 12 Aug 2019 10:56:23 -0400 Received: by mail-pg1-f195.google.com with SMTP id t132so49610431pgb.9 for ; Mon, 12 Aug 2019 07:56:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=3NQFlI4lPYDkvZgs+SnZFXq303TlZRy3bgOdazYblNc=; b=NQ/9B5p6EJnc/jGagbLM/8utrsVRGSqpApLAwGccX5pyS3J/WcnaL76DY5ZPmNj/me +sOQkXutAriyMqi+oLObLZvGQLAia8jcHXEZ76S2/2iX/m6q9ZxUBAuq6hc8fExbhUE5 WykTmRJksJRkfuwSeyqAdKimKYBeiv/vOihXA= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=3NQFlI4lPYDkvZgs+SnZFXq303TlZRy3bgOdazYblNc=; b=Q7nVl5cIHHZrWq1xH3bWP/rgThOhUx3f1kbFHkLrMhbNJR+iFE5917vDTb2tsoDSkS z1G1dzCxqFYEdnTBpBwQfmnOwGwQRPZMGYRxQ459caOb7PmaXK02NW3tZwwknaR2/NTq v/jxa+QM+o/rux3+DIxAE/cwDbX+V8moap0vMi/tNjij4f6s+RpYWEQpcjgnthezFChE xVPDjIbpK62x8Te4mWEw+8wqFXjySG/GyNUMDR6neMPDR//MrD+1SH1UThuRt6cd1QlO 9j0vD0e/yHybOFPD4AADR4u8uu4zeVdE9fM5NWeOjwhCdZ9dwgGeEsSNPEBtFx1JVuMd gyeA== X-Gm-Message-State: APjAAAW2RoDCVGohofAZJ6o9JPx/2j6FVZcmENmTFw/sOpWDiCNGulED bingYuYFO/+1PwqS3xiRDhP5DQ== X-Google-Smtp-Source: APXvYqwENYmtyILjOnl4HilVvOmaVrKuBkJ28bAMVAwHSpsNFJRH+v3wmBUJf3pYNep/OXJa+KX7pQ== X-Received: by 2002:a65:4786:: with SMTP id e6mr29905703pgs.448.1565621782717; Mon, 12 Aug 2019 07:56:22 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id y23sm5052754pfr.86.2019.08.12.07.56.21 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 12 Aug 2019 07:56:21 -0700 (PDT) Date: Mon, 12 Aug 2019 10:56:20 -0400 From: Joel Fernandes To: Michal Hocko Cc: Andrew Morton , linux-kernel@vger.kernel.org, Alexey Dobriyan , 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 , minchan@kernel.org, namhyung@google.com, paulmck@linux.ibm.com, Robin Murphy , Roman Gushchin , Stephen Rothwell , surenb@google.com, Thomas Gleixner , tkjos@google.com, Vladimir Davydov , Vlastimil Babka , Will Deacon Subject: Re: [PATCH v5 1/6] mm/page_idle: Add per-pid idle page tracking using virtual index Message-ID: <20190812145620.GB224541@google.com> References: <20190807171559.182301-1-joel@joelfernandes.org> <20190807130402.49c9ea8bf144d2f83bfeb353@linux-foundation.org> <20190807204530.GB90900@google.com> <20190807135840.92b852e980a9593fe91fbf59@linux-foundation.org> <20190807213105.GA14622@google.com> <20190808080044.GA18351@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190808080044.GA18351@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, Aug 08, 2019 at 10:00:44AM +0200, Michal Hocko wrote: > On Wed 07-08-19 17:31:05, Joel Fernandes wrote: > > On Wed, Aug 07, 2019 at 01:58:40PM -0700, Andrew Morton wrote: > > > On Wed, 7 Aug 2019 16:45:30 -0400 Joel Fernandes wrote: > > > > > > > On Wed, Aug 07, 2019 at 01:04:02PM -0700, Andrew Morton wrote: > > > > > On Wed, 7 Aug 2019 13:15:54 -0400 "Joel Fernandes (Google)" wrote: > > > > > > > > > > > In Android, we are using this for the heap profiler (heapprofd) which > > > > > > profiles and pin points code paths which allocates and leaves memory > > > > > > idle for long periods of time. This method solves the security issue > > > > > > with userspace learning the PFN, and while at it is also shown to yield > > > > > > better results than the pagemap lookup, the theory being that the window > > > > > > where the address space can change is reduced by eliminating the > > > > > > intermediate pagemap look up stage. In virtual address indexing, the > > > > > > process's mmap_sem is held for the duration of the access. > > > > > > > > > > So is heapprofd a developer-only thing? Is heapprofd included in > > > > > end-user android loads? If not then, again, wouldn't it be better to > > > > > make the feature Kconfigurable so that Android developers can enable it > > > > > during development then disable it for production kernels? > > > > > > > > Almost all of this code is already configurable with > > > > CONFIG_IDLE_PAGE_TRACKING. If you disable it, then all of this code gets > > > > disabled. > > > > > > > > Or are you referring to something else that needs to be made configurable? > > > > > > Yes - the 300+ lines of code which this patchset adds! > > > > > > The impacted people will be those who use the existing > > > idle-page-tracking feature but who will not use the new feature. I > > > guess we can assume this set is small... > > > > Yes, I think this set should be small. The code size increase of page_idle.o > > is from ~1KB to ~2KB. Most of the extra space is consumed by > > page_idle_proc_generic() function which this patch adds. I don't think adding > > another CONFIG option to disable this while keeping existing > > CONFIG_IDLE_PAGE_TRACKING enabled, is worthwhile but I am open to the > > addition of such an option if anyone feels strongly about it. I believe that > > once this patch is merged, most like this new interface being added is what > > will be used more than the old interface (for some of the usecases) so it > > makes sense to keep it alive with CONFIG_IDLE_PAGE_TRACKING. > > I would tend to agree with Joel here. The functionality falls into an > existing IDLE_PAGE_TRACKING config option quite nicely. If there really > are users who want to save some space and this is standing in the way > then they can easily add a new config option with some justification so > the savings are clear. Without that an additional config simply adds to > the already existing configurability complexity and balkanization. Michal, Andrew, Minchan, Would you have any other review comments on the v5 series? This is just a new interface that does not disrupt existing users of the older page-idle tracking, so as such it is a safe change (as in, doesn't change existing functionality except for the draining bug fix). thanks, - Joel