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[209.85.220.65]) by mx.google.com with SMTPS id d6sor72286524pfd.59.2019.08.07.14.55.51 for (Google Transport Security); Wed, 07 Aug 2019 14:55:51 -0700 (PDT) Received-SPF: pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@joelfernandes.org header.s=google header.b=iLFial3W; spf=pass (google.com: domain of joel@joelfernandes.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=joel@joelfernandes.org 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=fPDNifyL3Y36NBVemhHSXF79qGomK0S4tenrlniMG8c=; b=iLFial3WG2Y7hC5RmH/BPZMbk7K/mSRsub86lIBJhU4yCFb7muLzqQlM2Rw/ElKGgC SFjKYwdRoliyNAlbyClW8nV7pvHzWz0n8BGIO7Li2Qvwc3w0FvMgmdrCGjAVrSK9JbBy BL0fPr4WaEXa+YoPzJ+O512HUakd8rmUXyXUM= X-Google-Smtp-Source: APXvYqxtYbX1J2T4gE/+OoiVyWtnb2A4+C1faUKsGzqUpJz/BeHl7Ul7v7RUi0zJvoSnKkCTeSkNNg== X-Received: by 2002:aa7:9afc:: with SMTP id y28mr11421501pfp.252.1565214951446; Wed, 07 Aug 2019 14:55:51 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id z4sm79672843pgp.80.2019.08.07.14.55.50 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 07 Aug 2019 14:55:50 -0700 (PDT) Date: Wed, 7 Aug 2019 17:55:49 -0400 From: Joel Fernandes To: Andrew Morton Cc: 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, Michal Hocko , 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: <20190807215549.GB14622@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190807213105.GA14622@google.com> 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 Wed, Aug 07, 2019 at 05:31:05PM -0400, 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 s/most like/most likely/ > 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. > > thanks, > > - Joel >