From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1522653101; cv=none; d=google.com; s=arc-20160816; b=qzwrYKQ19fZY4P34CGDeONeJ7LBX1PxrzSssynxuzxcCm35UDUJZxxGPv/n/tB3gT5 TQTDjEZvJCGBiOcZfYwVM1auVDIkYqwy636xKh0IPF1sK/CV0YALPyBYP0TiidGwVh1W oX9ctqxf3CmvQbPSpK9Id3e+0mN3A4kxh/cvmLq6Ge9Vgb51qxoKY0cw9PkhjFcyLSF7 ZAcXiNBBAixj+fGb3nQ5wF//ObleeMz0UYTUMykO6Gh1xZkHjCOjaQRfPLEm1tBYkcQL DUTDU3JGqljJjzCW3GrYX7lwSEDHRHC1KxvXDbuPFH/395odLYsqTWImd3sMbHXHFhvp PyGA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:sender:dkim-signature :arc-authentication-results; bh=USK8weOBojMRp/5oYi/VxDiJXwY+fCbzOW6XaF/xbGQ=; b=aJshE0LXaLMoYnB/Q80L5lRbuAyT/gWtfESF93fQpQU5mKGUh13XqBjfXWbSOJtaD1 TUC/GLJ8rzST8hWSEBmI1N6oHILiA9s7VSDRwFcc1Xuk3GqWv5W6q/XouPVhKCzYJzax a23IPYYaiGE6QsP29Vz72ot+zxRoJ/V4sSThO0I1lzQfW6oJBJFyCwTXMDTyx5qt/N8z L0Z7syfak7CSlHCqgxiLQNPUc9ncHlxokZpE8ReLY+gUgFPcKYxSkDnNPIWYjOeTOYeM q5SM2G4/eS7BRCywgTZudePEEfHii2WkO1QM8xTIJYD8G/XTTsDFL1hxaVAz6fNaJt6W btpA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=p/cSt4g9; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=p/cSt4g9; spf=pass (google.com: domain of minchan.kim@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com X-Google-Smtp-Source: AIpwx49bcGyhRFfHvijwy90RtNG3TJhA0mIJBWXzZr8/boUuo3Ae/0wmLIGECufO11d232hA0cc0gA== Sender: Minchan Kim Date: Mon, 2 Apr 2018 16:11:33 +0900 From: Minchan Kim To: Ganesh Mahendran Cc: Greg Kroah-Hartman , LKML , Joe Perches , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Todd Kjos , Martijn Coenen Subject: Re: [PATCH v5] ANDROID: binder: change down_write to down_read Message-ID: <20180402071133.GA62369@rodete-desktop-imager.corp.google.com> References: <20180329065424.203172-1-minchan@kernel.org> <20180330012921.GB255979@rodete-desktop-imager.corp.google.com> <20180330100407.GB19140@kroah.com> <20180402063448.GA250086@rodete-desktop-imager.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596254032587353794?= X-GMAIL-MSGID: =?utf-8?q?1596617498845791956?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, Apr 02, 2018 at 02:46:14PM +0800, Ganesh Mahendran wrote: > 2018-04-02 14:34 GMT+08:00 Minchan Kim : > > On Fri, Mar 30, 2018 at 12:04:07PM +0200, Greg Kroah-Hartman wrote: > >> On Fri, Mar 30, 2018 at 10:29:21AM +0900, Minchan Kim wrote: > >> > Hi Ganesh, > >> > > >> > On Fri, Mar 30, 2018 at 09:21:55AM +0800, Ganesh Mahendran wrote: > >> > > 2018-03-29 14:54 GMT+08:00 Minchan Kim : > >> > > > binder_update_page_range needs down_write of mmap_sem because > >> > > > vm_insert_page need to change vma->vm_flags to VM_MIXEDMAP unless > >> > > > it is set. However, when I profile binder working, it seems > >> > > > every binder buffers should be mapped in advance by binder_mmap. > >> > > > It means we could set VM_MIXEDMAP in binder_mmap time which is > >> > > > already hold a mmap_sem as down_write so binder_update_page_range > >> > > > doesn't need to hold a mmap_sem as down_write. > >> > > > > >> > > > Android suffers from mmap_sem contention so let's reduce mmap_sem > >> > > > down_write. > >> > > > >> > > Hi, Minchan: > >> > > > >> > > It seems there is performance regression of this patch. > >> > > >> > You mean "This patch aims for solving performance regression" not "This patch > >> > makes performance regression"? > >> > > >> > > > >> > > Do you have some test result of android app launch time or binderThroughput? > >> > > >> > Unfortunately, I don't have any number. The goal is to reduce the number of > >> > call mmap_sem as write-side lock because it makes priority inversion of threads > >> > easily and that's one of clear part I spot that we don't need write-side lock. > >> > >> Please always run the binderThroughput tests when making binder changes > >> (there is a binder test suite in the CTS Android tests), as that ensures > >> that you are not causing performance regressions as well as just normal > >> bug regressions :) > > > > Thanks for the information. I didn't notice that such kinds of tests for > > binder. I will keep it in mind. > > > > Today, I have setup the testing for my phone and found testing was very > > fluctuating even without my patch. It might be not good with my test > > skill. I emulated user's behavior with various touch event. With it, I open > > various apps and play with them several times. Before starting the test, > > I did "adb shell stop && adb shell start && echo 3 > /proc/sys/vm/drop_caches" > > > > Such 15% noise was very easy to make it. > > > > Ganesh, How did you measure? What's the stddev? > > Hi, Minchan: > > Sorry for the late response, a little busy these days. :) > > We have our own test tools to measure app launch time, or you can use > android systrace to get the app launch time. We tested your V1 patch: > https://patchwork.kernel.org/patch/10312057/ > and found app lunch time regression. V1 had a bug with VM_MAYWRITE. Could you confirm it with v5? Please tell me more detail. What apps are slower compared to old? Every apps are slowed with avg 15%? Then, what's the stddev? The reason I'm asking is as I mentioned, it would be caused by rw_semaphore implementation and priority of threads which calls binder operation so I guess it would be not deterministic. When I had an simple experiment, it was very fluctuating as I expected. (the testing enviroment might be not good in my side). If it's real problem on real practice, better fix is not using write_lock of mmap_sem(it's abusing the write-side lock) but should adjust priority, I think. What do you think? Anyway, before the further discussion, we should confirm the root cause. > > I will use binderThroghput tool to test the patch today or tomorrow. > Thanks. I will do.