From: Minchan Kim <minchan@kernel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: "Huang, Ying" <ying.huang@intel.com>,
Rik van Riel <riel@redhat.com>, Michal Hocko <mhocko@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
Vinayak Menon <vinmenon@codeaurora.org>,
Mel Gorman <mgorman@suse.de>,
Andrew Morton <akpm@linux-foundation.org>, <lkp@01.org>
Subject: Re: [LKP] [lkp] [mm] 5c0a85fad9: unixbench.score -6.3% regression
Date: Tue, 14 Jun 2016 17:57:28 +0900 [thread overview]
Message-ID: <20160614085728.GA2430@bbox> (raw)
In-Reply-To: <20160608085811.GB12655@black.fi.intel.com>
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" <ying.huang@intel.com> writes:
> >
> > > "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> 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.
next prev parent reply other threads:[~2016-06-14 8:57 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 2:27 [lkp] [mm] 5c0a85fad9: unixbench.score -6.3% regression kernel test robot
2016-06-06 9:51 ` Kirill A. Shutemov
2016-06-08 7:21 ` [LKP] " Huang, Ying
2016-06-08 8:41 ` Huang, Ying
2016-06-08 8:58 ` Kirill A. Shutemov
2016-06-12 0:49 ` Huang, Ying
2016-06-12 1:02 ` Linus Torvalds
2016-06-13 9:02 ` Huang, Ying
2016-06-14 13:38 ` Minchan Kim
2016-06-15 23:42 ` Huang, Ying
2016-06-13 12:52 ` Kirill A. Shutemov
2016-06-14 6:11 ` Linus Torvalds
2016-06-14 8:26 ` Kirill A. Shutemov
2016-06-14 16:07 ` Rik van Riel
2016-06-14 14:03 ` Christian Borntraeger
2016-06-14 8:57 ` Minchan Kim [this message]
2016-06-14 14:34 ` Kirill A. Shutemov
2016-06-15 23:52 ` Huang, Ying
2016-06-16 0:13 ` Minchan Kim
2016-06-16 22:27 ` Huang, Ying
2016-06-17 5:41 ` Minchan Kim
2016-06-17 19:26 ` Huang, Ying
2016-06-20 0:06 ` Minchan Kim
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