> On Mar 17, 2022, at 4:48 PM, Yang Shi <shy828301@xxxxxxxxx> wrote: > > > Changelog > v2: * Collected reviewed-by tags from Miaohe Lin. > * Fixed build error for patch 4/8. > > The readonly FS THP relies on khugepaged to collapse THP for suitable > vmas. But it is kind of "random luck" for khugepaged to see the > readonly FS vmas (see report: https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@xxxxxxx/) since currently the vmas are registered to khugepaged when: > - Anon huge pmd page fault > - VMA merge > - MADV_HUGEPAGE > - Shmem mmap > > If the above conditions are not met, even though khugepaged is enabled > it won't see readonly FS vmas at all. MADV_HUGEPAGE could be specified > explicitly to tell khugepaged to collapse this area, but when khugepaged > mode is "always" it should scan suitable vmas as long as VM_NOHUGEPAGE > is not set. > > So make sure readonly FS vmas are registered to khugepaged to make the > behavior more consistent. > > Registering the vmas in mmap path seems more preferred from performance > point of view since page fault path is definitely hot path. > > > The patch 1 ~ 7 are minor bug fixes, clean up and preparation patches. > The patch 8 converts ext4 and xfs. We may need convert more filesystems, > but I'd like to hear some comments before doing that. > > > Tested with khugepaged test in selftests and the testcase provided by > Vlastimil Babka in https://lore.kernel.org/lkml/df3b5d1c-a36b-2c73-3e27-99e74983de3a@xxxxxxx/ > by commenting out MADV_HUGEPAGE call. LGTM. For the series: Acked-by: Song Liu <song@xxxxxxxxxx> > > > b/fs/ext4/file.c | 4 +++ > b/fs/xfs/xfs_file.c | 4 +++ > b/include/linux/huge_mm.h | 9 +++++++ > b/include/linux/khugepaged.h | 69 +++++++++++++++++++++---------------------------------------- > b/include/linux/sched/coredump.h | 3 +- > b/kernel/fork.c | 4 --- > b/mm/huge_memory.c | 15 +++---------- > b/mm/khugepaged.c | 71 ++++++++++++++++++++++++++++++++++++++++++++------------------- > b/mm/shmem.c | 14 +++--------- > 9 files changed, 102 insertions(+), 91 deletions(-) >
