From: Lance Yang <ioworker0@gmail.com> mainline inclusion from mainline-v6.11-rc1 commit 9b89e018990de47c72ef8b2ca29204f88fda8f05 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IAIHPC Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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 <mingzhe.yang@ly.com> Signed-off-by: Lance Yang <ioworker0@gmail.com> Reviewed-by: Barry Song <baohua@kernel.org> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Bang Li <libang.li@antgroup.com> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Yang Shi <shy828301@gmail.com> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Liu Shixin <liushixin2@huawei.com> --- Documentation/admin-guide/mm/transhuge.rst | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 89e124d66ceb..13e09977c43a 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -397,10 +397,6 @@ 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 @@ -542,6 +538,21 @@ 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 -- 2.25.1