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. + +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
