On 11/27/18 6:08 PM, Linus Torvalds wrote: > On Mon, Nov 26, 2018 at 10:24 PM kernel test robot > <[email protected]> wrote: >> >> FYI, we noticed a -61.3% regression of vm-scalability.throughput due >> to commit ac5b2c18911f ("mm: thp: relax __GFP_THISNODE for >> MADV_HUGEPAGE mappings") > > Well, that's certainly noticeable and not good. > > Andrea, I suspect it might be causing fights with auto numa migration.. > > Lots more system time, but also look at this: > >> 1122389 ± 9% +17.2% 1315380 ± 4% proc-vmstat.numa_hit >> 214722 ± 5% +21.6% 261076 ± 3% >> proc-vmstat.numa_huge_pte_updates >> 1108142 ± 9% +17.4% 1300857 ± 4% proc-vmstat.numa_local >> 145368 ± 48% +63.1% 237050 ± 17% proc-vmstat.numa_miss >> 159615 ± 44% +57.6% 251573 ± 16% proc-vmstat.numa_other >> 185.50 ± 81% +8278.6% 15542 ± 40% proc-vmstat.numa_pages_migrated > > Should the commit be reverted? Or perhaps at least modified?
This part of the test's config is important: thp_defrag: always While the commit targets MADV_HUGEPAGE mappings (such as Andrea's kvm-qemu usecase), with defrag=always, all mappings behave almost as a MADV_HUGEPAGE mapping. That's no longer a default for some years now and I think nobody recommends it. In the default configuration nothing changes for non-madvise mappings. Vlastimil > Linus >
