"Kirill A. Shutemov" <[email protected]> writes: > 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" <[email protected]> writes: >> > > >> > > > "Kirill A. Shutemov" <[email protected]> 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?
We put root file system and benchmark into a set of compressed cpio archive, then concatenate them into one initrd, and finally kernel use that initrd as initramfs. Best Regards, Huang, Ying
