On Fri, Apr 04, 2025 at 06:31:16PM +0200, Pankaj Raghav (Samsung) wrote: > On Fri, Apr 04, 2025 at 08:32:15AM -0700, Luis Chamberlain wrote: > > On Fri, Apr 04, 2025 at 04:06:57PM +0200, Pankaj Raghav (Samsung) wrote: > > > From: Pankaj Raghav <p.raghav@xxxxxxxxxxx> > > > > > > THP support for non-tmpfs filesystem has been around for some time now. > > > Update the admin guide to reflect it. > > > > > > While we are at it, move FilePmdMapped to previous paragraph for clarity, > > > and clarify ShmemPmdMapped & ShmemHugePage. > > > > > > Signed-off-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx> > > > Acked-by: David Hildenbrand <david@xxxxxxxxxx> > > > --- > > > > > > Changes since v2: > > > - Address comment from Bagas Sanjaya > > > - Squash commits and Ack from David > > > > > > Documentation/admin-guide/mm/transhuge.rst | 22 +++++++++++++++------- > > > 1 file changed, 15 insertions(+), 7 deletions(-) > > > > > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > > > index dff8d5985f0f..f8aae64e38d0 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. > > > > That seems to allude that THP can be supported on filesystems > > that suppor large folios. I don't think we want to call that THP > > But we do allocate a THP in the page cache if we support large folios. > > See [1] where THP was supported through page cache. From what I > understand, THP support was added first to the page cache and then large > folios (orders in between) support came later. I see, yes Do we want to clarify this further? > For example, you can mount XFS and do a simple dd as follows: > > $ dd if=/dev/random of=/mnt/hello bs=1G count=2 > > And if you monitor `FileHugePages` after dd is done, it would have filled > up if THP is enabled. > > > and that can confuse folks. Leaving "currently" also seems to > > indicate that there is more work to be done for THP for filesystems > > but that's not true as well. So how about something like: > > There is more work to be done in the filesystems right? Adding large > folio support is the prerequisite here to get the THP support. This would be good to clarify as well. Luis
