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=ham 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 678F57D2F0 for ; Wed, 7 Aug 2019 21:31:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389313AbfHGVbJ (ORCPT ); Wed, 7 Aug 2019 17:31:09 -0400 Received: from mail-pf1-f196.google.com ([209.85.210.196]:36498 "EHLO mail-pf1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730180AbfHGVbI (ORCPT ); Wed, 7 Aug 2019 17:31:08 -0400 Received: by mail-pf1-f196.google.com with SMTP id r7so42819013pfl.3 for ; Wed, 07 Aug 2019 14:31:08 -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=NQJ8f3sbtpxQFwytiN3eHpksnWvvNOcO2e4/JMupkqc=; b=ltUuSGLnwli7uHEKMbcJ+YOm7vx0HT8aK0FqET7xYC6vzOpSEUHRN/AATglHk0+0p+ zSnAx29U8WuLTI9ExqxwFzPZmo0mHUqAjMn2RgZOIpvSFf2FTljKhjOmlz/PX2bEMaRC lFE+Jq8IidL4IM+nVDmMMflaOTHFIJmzC3aOM= 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=NQJ8f3sbtpxQFwytiN3eHpksnWvvNOcO2e4/JMupkqc=; b=W283OHtmfo9WvgdHNXcFkwdpT+ww1BKThM8VxUqTLSggyC1fcmXoYzu1hx8sCT+REQ JrUPCLZnySFGj7lYGmpLWR1VIW0+Tg255HzjWmyZt9CZ/5llfcM96cr6nCWQe8z4qCwC 7ZTnN6KSotuDVg6DHn05t1wJhBa5HOnZtX3WRR38APOkxYxIZ2778frL+CdAVYTaG8m9 35y0+A46XWPy6CzzNEV2yq02hGIhVFsNX2Ozb5ZfS/bJY56sPYbtLNlTasiDaATJKDGa qyazRDMS0qESEAsk+qS/PdX0uAFQUPsVL52zhLlg+z/x0smeGz0wOCXnJQtqAJ3QSV16 yMxg== X-Gm-Message-State: APjAAAWwIywBtRFPV+BhUexP1ejF/RavGzigx4WvjSea9MwZE6WUfJjn Q7TNcZSanNl5miz/sosPv/byfQ== X-Google-Smtp-Source: APXvYqycwCSZRxiQZg5b6w8u5vo5c0fzV5zhn+ILS/tJqsI66etCit/pYaYlIq/y8q2Rld0VAf6CWw== X-Received: by 2002:aa7:91cc:: with SMTP id z12mr11549407pfa.76.1565213468077; Wed, 07 Aug 2019 14:31:08 -0700 (PDT) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id a6sm92456750pfa.162.2019.08.07.14.31.06 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Wed, 07 Aug 2019 14:31:07 -0700 (PDT) Date: Wed, 7 Aug 2019 17:31:05 -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: <20190807213105.GA14622@google.com> References: <20190807171559.182301-1-joel@joelfernandes.org> <20190807130402.49c9ea8bf144d2f83bfeb353@linux-foundation.org> <20190807204530.GB90900@google.com> <20190807135840.92b852e980a9593fe91fbf59@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190807135840.92b852e980a9593fe91fbf59@linux-foundation.org> 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 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. thanks, - Joel