From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751876AbcFNOeY (ORCPT ); Tue, 14 Jun 2016 10:34:24 -0400 Received: from mail-lf0-f68.google.com ([209.85.215.68]:36766 "EHLO mail-lf0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750762AbcFNOeW (ORCPT ); Tue, 14 Jun 2016 10:34:22 -0400 Date: Tue, 14 Jun 2016 17:34:17 +0300 From: "Kirill A. Shutemov" To: Minchan Kim Cc: "Kirill A. Shutemov" , "Huang, Ying" , Rik van Riel , Michal Hocko , LKML , Linus Torvalds , Michal Hocko , Vinayak Menon , Mel Gorman , Andrew Morton , lkp@01.org Subject: Re: [LKP] [lkp] [mm] 5c0a85fad9: unixbench.score -6.3% regression Message-ID: <20160614143417.GC3571@node.shutemov.name> References: <20160606022724.GA26227@yexl-desktop> <20160606095136.GA79951@black.fi.intel.com> <87a8iw5enf.fsf@yhuang-dev.intel.com> <8760tk5aym.fsf@yhuang-dev.intel.com> <20160608085811.GB12655@black.fi.intel.com> <20160614085728.GA2430@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160614085728.GA2430@bbox> 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 Tue, Jun 14, 2016 at 05:57:28PM +0900, Minchan Kim wrote: > On Wed, Jun 08, 2016 at 11:58:11AM +0300, Kirill A. Shutemov wrote: > > 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. > > Hmm, tmpfs pages should be in anonymous LRU list and VM shouldn't scan > anonymous LRU list on swapless system so I really wonder why active file > LRU is shrunk. Hm. Good point. I don't why we have anything on file lru if there's no filesystems except tmpfs. Ying, how do you get stuff to the tmpfs? -- Kirill A. Shutemov