Commit b7e9a1a5 authored by Lance Yang's avatar Lance Yang Committed by Liu Shixin
Browse files

mm: add docs for per-order mTHP split counters 

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/?id=9b89e018990de47c72ef8b2ca29204f88fda8f05

--------------------------------

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: default avatarMingzhe Yang <mingzhe.yang@ly.com>
Signed-off-by: default avatarLance Yang <ioworker0@gmail.com>
Reviewed-by: default avatarBarry Song <baohua@kernel.org>
Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Acked-by: default avatarDavid 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 7e9c56da

Documentation/admin-guide/mm/transhuge.rst

+15 −4
Original line number Diff line number Diff line
@@ -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