On 04/07/2024 02:29, Lance Yang wrote: > This commit introduces documentation for mTHP split counters in > transhuge.rst. > > Reviewed-by: Barry Song <baohua@xxxxxxxxxx> > Signed-off-by: Mingzhe Yang <mingzhe.yang@xxxxxx> > Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx> > --- > Documentation/admin-guide/mm/transhuge.rst | 20 ++++++++++++++++---- > 1 file changed, 16 insertions(+), 4 deletions(-) > > diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst > index 1f72b00af5d3..0830aa173a8b 100644 > --- a/Documentation/admin-guide/mm/transhuge.rst > +++ b/Documentation/admin-guide/mm/transhuge.rst > @@ -369,10 +369,6 @@ also applies to the regions registered in khugepaged. > Monitoring usage > ================ > > -.. note:: > - Currently the below counters only record events relating to > - PMD-sized THP. Events relating to other THP sizes are not included. > - > The number of PMD-sized anonymous transparent huge pages currently used by the > system is available by reading the AnonHugePages field in ``/proc/meminfo``. > To identify what applications are using PMD-sized anonymous transparent huge > @@ -514,6 +510,22 @@ 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 > + smaller orders. 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. nit: the block mappings will already be PTEs if starting with mTHP? regardless: Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx> > + > +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
