Messages in this thread | | | Subject | Re: [v3 PATCH 0/2] Fix false negative of shmem vma's THP eligibility | From | Yang Shi <> | Date | Mon, 15 Jul 2019 12:49:19 -0700 |
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Hi Hugh,
Any comments for this version? Although they have been in -mm tree, they didn't make in 5.3 merge window, I'm supposed Andrew needs ack from you or someone else.
Thanks,
Yang
On 6/12/19 9:43 PM, Yang Shi wrote: > The commit 7635d9cbe832 ("mm, thp, proc: report THP eligibility for each > vma") introduced THPeligible bit for processes' smaps. But, when checking > the eligibility for shmem vma, __transparent_hugepage_enabled() is > called to override the result from shmem_huge_enabled(). It may result > in the anonymous vma's THP flag override shmem's. For example, running a > simple test which create THP for shmem, but with anonymous THP disabled, > when reading the process's smaps, it may show: > > 7fc92ec00000-7fc92f000000 rw-s 00000000 00:14 27764 /dev/shm/test > Size: 4096 kB > ... > [snip] > ... > ShmemPmdMapped: 4096 kB > ... > [snip] > ... > THPeligible: 0 > > And, /proc/meminfo does show THP allocated and PMD mapped too: > > ShmemHugePages: 4096 kB > ShmemPmdMapped: 4096 kB > > This doesn't make too much sense. The shmem objects should be treated > separately from anonymous THP. Calling shmem_huge_enabled() with checking > MMF_DISABLE_THP sounds good enough. And, we could skip stack and > dax vma check since we already checked if the vma is shmem already. > > The transhuge_vma_suitable() is needed to check vma, but it was only > available for shmem THP. The patch 1/2 makes it available for all kind of > THPs and does some code duplication cleanup, so it is made a separate patch. > > > Changelog: > v3: * Check if vma is suitable for allocating THP per Hugh Dickins > * Fixed smaps output alignment and documentation per Hugh Dickins > v2: * Check VM_NOHUGEPAGE per Michal Hocko > > > Yang Shi (2): > mm: thp: make transhuge_vma_suitable available for anonymous THP > mm: thp: fix false negative of shmem vma's THP eligibility > > Documentation/filesystems/proc.txt | 4 ++-- > fs/proc/task_mmu.c | 3 ++- > mm/huge_memory.c | 11 ++++++++--- > mm/internal.h | 25 +++++++++++++++++++++++++ > mm/memory.c | 13 ------------- > mm/shmem.c | 3 +++ > 6 files changed, 40 insertions(+), 19 deletions(-)
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