[PATCH v5 4/4] mm: correct the docs for thp_fault_alloc and thp_fault_fallback

From: Barry Song
Date: Fri Apr 12 2024 - 03:38:51 EST


From: Barry Song <v-songbaohua@xxxxxxxx>

The documentation does not align with the code. In
__do_huge_pmd_anonymous_page(), THP_FAULT_FALLBACK is incremented when
mem_cgroup_charge() fails, despite the allocation succeeding, whereas
THP_FAULT_ALLOC is only incremented after a successful charge.

Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
---
Documentation/admin-guide/mm/transhuge.rst | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index f436ff982f22..98e3a99ea780 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -369,7 +369,7 @@ monitor how successfully the system is providing huge pages for use.

thp_fault_alloc
is incremented every time a huge page is successfully
- allocated to handle a page fault.
+ allocated and charged to handle a page fault.

thp_collapse_alloc
is incremented by khugepaged when it has found
@@ -377,7 +377,7 @@ thp_collapse_alloc
successfully allocated a new huge page to store the data.

thp_fault_fallback
- is incremented if a page fault fails to allocate
+ is incremented if a page fault fails to allocate or charge
a huge page and instead falls back to using small pages.

thp_fault_fallback_charge
--
2.34.1