Minchan Kim <[email protected]> wrote: > Hi, > > On Tue, Aug 08, 2017 at 09:19:23AM +0800, kernel test robot wrote: >> Greeting, >> >> FYI, we noticed a -19.3% regression of will-it-scale.per_process_ops due to >> commit: >> >> >> commit: 76742700225cad9df49f05399381ac3f1ec3dc60 ("mm: fix >> MADV_[FREE|DONTNEED] TLB flush miss problem") >> url: >> https://github.com/0day-ci/linux/commits/Nadav-Amit/mm-migrate-prevent-racy-access-to-tlb_flush_pending/20170802-205715 >> >> >> in testcase: will-it-scale >> on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with >> 64G memory >> with following parameters: >> >> nr_task: 16 >> mode: process >> test: brk1 >> cpufreq_governor: performance >> >> test-description: Will It Scale takes a testcase and runs it from 1 through >> to n parallel copies to see if the testcase will scale. It builds both a >> process and threads based test in order to see any differences between the >> two. >> test-url: https://github.com/antonblanchard/will-it-scale > > Thanks for the report. > Could you explain what kinds of workload you are testing? > > Does it calls frequently madvise(MADV_DONTNEED) in parallel on multiple > threads?
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. Nadav
