From: Lance Yang Date: Fri, 28 Jun 2024 13:07:50 +0000 (+0800) Subject: mm: add docs for per-order mTHP split counters X-Git-Tag: v6.11-rc1~85^2~55 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9b89e018990de47c72ef8b2ca29204f88fda8f05;p=thirdparty%2Fkernel%2Flinux.git mm: add docs for per-order mTHP split counters This commit introduces documentation for mTHP split counters in transhuge.rst. [ioworker0@gmail.com: improve the doc as suggested by Ryan] Link: https://lkml.kernel.org/r/20240704012905.42971-3-ioworker0@gmail.com [ioworker0@gmail.com: tweak Documentation/admin-guide/mm/transhuge.rst] Link: https://lkml.kernel.org/r/20240707013659.1151-1-ioworker0@gmail.com Link: https://lkml.kernel.org/r/20240628130750.73097-3-ioworker0@gmail.com Signed-off-by: Mingzhe Yang Signed-off-by: Lance Yang Reviewed-by: Barry Song Reviewed-by: Ryan Roberts Acked-by: David Hildenbrand Cc: Bang Li Cc: Baolin Wang Cc: Yang Shi Cc: Zi Yan Signed-off-by: Andrew Morton --- diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 1f72b00af5d35..a1bc9b24e29ab 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 +510,21 @@ 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. + +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, if splitting is possible. + 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