On Wed, Aug 09, 2017 at 09:14:50PM -0700, Nadav Amit wrote: Hi Nadav, < snip > > >>>>> According to the description it is "testcase:brk increase/decrease of one > >>>>> page”. According to the mode it spawns multiple processes, not threads. > >>>>> > >>>>> Since a single page is unmapped each time, and the iTLB-loads increase > >>>>> dramatically, I would suspect that for some reason a full TLB flush is > >>>>> caused during do_munmap(). > >>>>> > >>>>> If I find some free time, I’ll try to profile the workload - but feel free > >>>>> to beat me to it. > >>>> > >>>> The root-cause appears to be that tlb_finish_mmu() does not call > >>>> dec_tlb_flush_pending() - as it should. Any chance you can take care of it? > >>> > >>> Oops, but with second looking, it seems it's not my fault. ;-) > >>> https://marc.info/?l=linux-mm&m=150156699114088&w=2 > >>> > >>> Anyway, thanks for the pointing out. > >>> xiaolong.ye, could you retest with this fix? > >> > >> I've queued tests for 5 times and results show this patch (e8f682574e4 "mm: > >> decrease tlb flush pending count in tlb_finish_mmu") does help recover the > >> performance back. > >> > >> 378005bdbac0a2ec 76742700225cad9df49f053993 e8f682574e45b6406dadfffeb4 > >> ---------------- -------------------------- -------------------------- > >> %stddev change %stddev change %stddev > >> \ | \ | \ > >> 3405093 -19% 2747088 -2% 3348752 will-it-scale.per_process_ops > >> 1280 ± 3% -2% 1257 ± 3% -6% 1207 vmstat.system.cs > >> 2702 ± 18% 11% 3002 ± 19% 17% 3156 ± 18% numa-vmstat.node0.nr_mapped > >> 10765 ± 18% 11% 11964 ± 19% 17% 12588 ± 18% numa-meminfo.node0.Mapped > >> 0.00 ± 47% -40% 0.00 ± 45% -84% 0.00 ± 42% mpstat.cpu.soft% > >> > >> Thanks, > >> Xiaolong > > > > Thanks for the testing! > > Sorry again for screwing your patch, Minchan. Never mind! It always happens. :) In this chance, I really appreciates your insight/testing/cooperation!
