Re: [PATCH v2 2/2] mm: add docs for per-order mTHP split counters
From: Lance Yang
Date: Sat Jun 29 2024 - 10:30:27 EST
Hi Barry,
Thanks a lot for taking time to review!
On Sat, Jun 29, 2024 at 11:08 AM Barry Song <21cnbao@xxxxxxxxx> wrote:
>
> On Sat, Jun 29, 2024 at 1:09 AM Lance Yang <ioworker0@xxxxxxxxx> wrote:
> >
> > This commit introduces documentation for mTHP split counters in
> > transhuge.rst.
> >
> > Signed-off-by: Mingzhe Yang <mingzhe.yang@xxxxxx>
> > Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
>
> Reviewed-by: Barry Song <baohua@xxxxxxxxxx>
Have a nice weekend ;)
Lance
>
> > ---
> > Documentation/admin-guide/mm/transhuge.rst | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> > index 1f72b00af5d3..709fe10b60f4 100644
> > --- a/Documentation/admin-guide/mm/transhuge.rst
> > +++ b/Documentation/admin-guide/mm/transhuge.rst
> > @@ -514,6 +514,22 @@ file_fallback_charge
> > falls back to using small pages even though the allocation was
> > successful.
> >
> > +split
> > + is incremented every time a huge page is successfully split into
> > + base pages. This can happen for a variety of reasons but a common
> > + reason is that a huge page is old and is being reclaimed.
> > + This action implies splitting any block mappings into PTEs.
> > +
> > +split_failed
> > + is incremented if kernel fails to split huge
> > + page. This can happen if the page was pinned by somebody.
> > +
> > +split_deferred
> > + is incremented when a huge page is put onto split
> > + queue. This happens when a huge page is partially unmapped and
> > + splitting it would free up some memory. Pages on split queue are
> > + going to be split under memory pressure.
> > +
> > As the system ages, allocating huge pages may be expensive as the
> > system uses memory compaction to copy data around memory to free a
> > huge page for use. There are some counters in ``/proc/vmstat`` to help
> > --
> > 2.45.2
> >