| Message ID | 20250403103805.173761-1-kernel@pankajraghav.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | docs: update THP admin guide about non-tmpfs filesystem support | expand |
On Thu, Apr 03, 2025 at 12:38:05PM +0200, Pankaj Raghav (Samsung) wrote: > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > index dff8d5985f0f..01b7ce90d693 100644 > --- a/Documentation/admin-guide/mm/transhuge.rst > +++ b/Documentation/admin-guide/mm/transhuge.rst > @@ -12,8 +12,8 @@ using huge pages for the backing of virtual memory with huge pages > that supports the automatic promotion and demotion of page sizes and > without the shortcomings of hugetlbfs. > > -Currently THP only works for anonymous memory mappings and tmpfs/shmem. > -But in the future it can expand to other filesystems. > +Currently, THP only works for anonymous memory mappings, tmpfs/shmem and > +filesystems that support large folios. > > .. note:: > in the examples below we presume that the basic page size is 4K and > @@ -463,6 +463,10 @@ fields for each mapping. (Note that AnonHugePages only applies to traditional > PMD-sized THP for historical reasons and should have been called > AnonHugePmdMapped). > > +The number of PMD-sized transparent huge pages currently used by > +filesystem data (page cache) is available by reading the FileHugePages field > +in ``/proc/meminfo``. > + > The number of file transparent huge pages mapped to userspace is available > by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``. > To identify what applications are mapping file transparent huge pages, it > > base-commit: f0a16f5363325cc8d9382471cdc7b654c53254c9 The wording looks good, thanks! Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
On 03.04.25 12:38, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav <p.raghav@samsung.com> > > THP support for non-tmpfs filesystem has been around for some time now. > Update the admin guide to reflect it. > > Signed-off-by: Pankaj Raghav <p.raghav@samsung.com> > --- > Documentation/admin-guide/mm/transhuge.rst | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > index dff8d5985f0f..01b7ce90d693 100644 > --- a/Documentation/admin-guide/mm/transhuge.rst > +++ b/Documentation/admin-guide/mm/transhuge.rst > @@ -12,8 +12,8 @@ using huge pages for the backing of virtual memory with huge pages > that supports the automatic promotion and demotion of page sizes and > without the shortcomings of hugetlbfs. > > -Currently THP only works for anonymous memory mappings and tmpfs/shmem. > -But in the future it can expand to other filesystems. > +Currently, THP only works for anonymous memory mappings, tmpfs/shmem and > +filesystems that support large folios. > > .. note:: > in the examples below we presume that the basic page size is 4K and > @@ -463,6 +463,10 @@ fields for each mapping. (Note that AnonHugePages only applies to traditional > PMD-sized THP for historical reasons and should have been called > AnonHugePmdMapped). > > +The number of PMD-sized transparent huge pages currently used by > +filesystem data (page cache) is available by reading the FileHugePages field > +in ``/proc/meminfo``. > + These changed look good. Do we also want to talk about FilePmdMapped? (PMD-sized THPs in the page cache that are mapped in to user space using a PMD ?) Do we have to distinguish it from below? (shmem also uses the page cache) > The number of file transparent huge pages mapped to userspace is available > by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``. > To identify what applications are mapping file transparent huge pages, it Previously here, but: this reads rather odd. "file transparent huge pages". "PMD-sized THPs specific to shmem are tracked separately ..." ?
> > in the examples below we presume that the basic page size is 4K and > > @@ -463,6 +463,10 @@ fields for each mapping. (Note that AnonHugePages only applies to traditional > > PMD-sized THP for historical reasons and should have been called > > AnonHugePmdMapped). > > +The number of PMD-sized transparent huge pages currently used by > > +filesystem data (page cache) is available by reading the FileHugePages field > > +in ``/proc/meminfo``. > > + > > These changed look good. Do we also want to talk about FilePmdMapped? > (PMD-sized THPs in the page cache that are mapped in to user space using a > PMD ?) I am a bit new to this subsystem, and it took some time to wrap around all the different terminology used :) But sure, I will add a new commit to talk about FilePmdMapped. I can give it a shot with what I understand about FilePmdMapped, but please feel free to add your input. > > Do we have to distinguish it from below? (shmem also uses the page cache) > > > The number of file transparent huge pages mapped to userspace is available > > by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``. > > To identify what applications are mapping file transparent huge pages, it > > Previously here, but: this reads rather odd. "file transparent huge pages". > "PMD-sized THPs specific to shmem are tracked separately ..." ? > I totally agree. Reading "file transparent huge pages" confused me even more. I will fold these changes as well. Thanks, David. -- Pankaj
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index dff8d5985f0f..01b7ce90d693 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -12,8 +12,8 @@ using huge pages for the backing of virtual memory with huge pages that supports the automatic promotion and demotion of page sizes and without the shortcomings of hugetlbfs. -Currently THP only works for anonymous memory mappings and tmpfs/shmem. -But in the future it can expand to other filesystems. +Currently, THP only works for anonymous memory mappings, tmpfs/shmem and +filesystems that support large folios. .. note:: in the examples below we presume that the basic page size is 4K and @@ -463,6 +463,10 @@ fields for each mapping. (Note that AnonHugePages only applies to traditional PMD-sized THP for historical reasons and should have been called AnonHugePmdMapped). +The number of PMD-sized transparent huge pages currently used by +filesystem data (page cache) is available by reading the FileHugePages field +in ``/proc/meminfo``. + The number of file transparent huge pages mapped to userspace is available by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``. To identify what applications are mapping file transparent huge pages, it