Hello On Sun, 23 Jun 2019 13:48:47 +0800 Song Liu wrote: > This patch is (hopefully) the first step to enable THP for non-shmem > filesystems. > > This patch enables an application to put part of its text sections to THP > via madvise, for example: > > madvise((void *)0x600000, 0x200000, MADV_HUGEPAGE); > > We tried to reuse the logic for THP on tmpfs. > > Currently, write is not supported for non-shmem THP. khugepaged will only > process vma with VM_DENYWRITE. The next patch will handle writes, which > would only happen when the vma with VM_DENYWRITE is unmapped. > > An EXPERIMENTAL config, READ_ONLY_THP_FOR_FS, is added to gate this > feature. > > Acked-by: Rik van Riel <riel@xxxxxxxxxxx> > Signed-off-by: Song Liu <songliubraving@xxxxxx> > --- > mm/Kconfig | 11 ++++++ > mm/filemap.c | 4 +-- > mm/khugepaged.c | 90 ++++++++++++++++++++++++++++++++++++++++--------- > mm/rmap.c | 12 ++++--- > 4 files changed, 96 insertions(+), 21 deletions(-) > > diff --git a/mm/Kconfig b/mm/Kconfig > index f0c76ba47695..0a8fd589406d 100644 > --- a/mm/Kconfig > +++ b/mm/Kconfig > @@ -762,6 +762,17 @@ config GUP_BENCHMARK > > See tools/testing/selftests/vm/gup_benchmark.c > > +config READ_ONLY_THP_FOR_FS > + bool "Read-only THP for filesystems (EXPERIMENTAL)" > + depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM > + The ext4 mentioned in the cover letter, along with the subject line of this patch, suggests the scissoring of SHMEM. > + help > + Allow khugepaged to put read-only file-backed pages in THP. > + > + This is marked experimental because it is a new feature. Write > + support of file THPs will be developed in the next few release > + cycles. > + > config ARCH_HAS_PTE_SPECIAL > bool Hillf
