From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932798AbcFHI6U (ORCPT ); Wed, 8 Jun 2016 04:58:20 -0400 Received: from mga11.intel.com ([192.55.52.93]:20201 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932551AbcFHI6R (ORCPT ); Wed, 8 Jun 2016 04:58:17 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,438,1459839600"; d="scan'208";a="993383340" Date: Wed, 8 Jun 2016 11:58:11 +0300 From: "Kirill A. Shutemov" To: "Huang, Ying" Cc: Rik van Riel , Michal Hocko , LKML , Linus Torvalds , Michal Hocko , Minchan Kim , Vinayak Menon , Mel Gorman , Andrew Morton , lkp@01.org Subject: Re: [LKP] [lkp] [mm] 5c0a85fad9: unixbench.score -6.3% regression Message-ID: <20160608085811.GB12655@black.fi.intel.com> References: <20160606022724.GA26227@yexl-desktop> <20160606095136.GA79951@black.fi.intel.com> <87a8iw5enf.fsf@yhuang-dev.intel.com> <8760tk5aym.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8760tk5aym.fsf@yhuang-dev.intel.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 08, 2016 at 04:41:37PM +0800, Huang, Ying wrote: > "Huang, Ying" writes: > > > "Kirill A. Shutemov" writes: > > > >> On Mon, Jun 06, 2016 at 10:27:24AM +0800, kernel test robot wrote: > >>> > >>> FYI, we noticed a -6.3% regression of unixbench.score due to commit: > >>> > >>> commit 5c0a85fad949212b3e059692deecdeed74ae7ec7 ("mm: make faultaround produce old ptes") > >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > >>> > >>> in testcase: unixbench > >>> on test machine: lituya: 16 threads Haswell High-end Desktop (i7-5960X 3.0G) with 16G memory > >>> with following parameters: cpufreq_governor=performance/nr_task=1/test=shell8 > >>> > >>> > >>> Details are as below: > >>> --------------------------------------------------------------------------------------------------> > >>> > >>> > >>> ========================================================================================= > >>> compiler/cpufreq_governor/kconfig/nr_task/rootfs/tbox_group/test/testcase: > >>> gcc-4.9/performance/x86_64-rhel/1/debian-x86_64-2015-02-07.cgz/lituya/shell8/unixbench > >>> > >>> commit: > >>> 4b50bcc7eda4d3cc9e3f2a0aa60e590fedf728c5 > >>> 5c0a85fad949212b3e059692deecdeed74ae7ec7 > >>> > >>> 4b50bcc7eda4d3cc 5c0a85fad949212b3e059692de > >>> ---------------- -------------------------- > >>> fail:runs %reproduction fail:runs > >>> | | | > >>> 3:4 -75% :4 kmsg.DHCP/BOOTP:Reply_not_for_us,op[#]xid[#] > >>> %stddev %change %stddev > >>> \ | \ > >>> 14321 . 0% -6.3% 13425 . 0% unixbench.score > >>> 1996897 . 0% -6.1% 1874635 . 0% unixbench.time.involuntary_context_switches > >>> 1.721e+08 . 0% -6.2% 1.613e+08 . 0% unixbench.time.minor_page_faults > >>> 758.65 . 0% -3.0% 735.86 . 0% unixbench.time.system_time > >>> 387.66 . 0% +5.4% 408.49 . 0% unixbench.time.user_time > >>> 5950278 . 0% -6.2% 5583456 . 0% unixbench.time.voluntary_context_switches > >> > >> That's weird. > >> > >> I don't understand why the change would reduce number or minor faults. > >> It should stay the same on x86-64. Rise of user_time is puzzling too. > > > > unixbench runs in fixed time mode. That is, the total time to run > > unixbench is fixed, but the work done varies. So the minor_page_faults > > change may reflect only the work done. > > > >> Hm. Is reproducible? Across reboot? > > > > And FYI, there is no swap setup for test, all root file system including > benchmark files are in tmpfs, so no real page reclaim will be > triggered. But it appears that active file cache reduced after the > commit. > > 111331 ± 1% -13.3% 96503 ± 0% meminfo.Active > 27603 ± 1% -43.9% 15486 ± 0% meminfo.Active(file) > > I think this is the expected behavior of the commit? Yes, it's expected. After the change faularound would produce old pte. It means there's more chance for these pages to be on inactive lru, unless somebody actually touch them and flip accessed bit. I wounder if this regression can attributed to cost of setting accessed bit. It looks too high, but who knows. I don't have time to do testing myself right now. I will put this on todo list. -- Kirill A. Shutemov