On 12.08.24 00:49, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx>
When an mTHP is added to the deferred_list, its partial pages
are unused, leading to wasted memory and potentially increasing
memory reclamation pressure.
Detailing the specifics of how unmapping occurs is quite difficult
and not that useful, so we adopt a simple approach: each time an
mTHP enters the deferred_list, we increment the count by 1; whenever
it leaves for any reason, we decrement the count by 1.
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
Documentation/admin-guide/mm/transhuge.rst | 5 +++++
include/linux/huge_mm.h | 1 +
mm/huge_memory.c | 6 ++++++
3 files changed, 12 insertions(+)
diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index 9fdfb46e4560..7072469de8a8 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -532,6 +532,11 @@ nr_anon
These huge pages could be entirely mapped or have partially
unmapped/unused subpages.
+nr_split_deferred
+ the number of anon huge pages which have been partially unmapped
+ and put onto split queue. Those unmapped subpages are also unused
+ and temporarily wasting memory.
The name suggests something else ... like a counter of how many have
been deferred split :)
Would "nr_anon_partially_mapped" "nr_anon_split_pending" (or something
less mouthful) be clearer?
(likely "anon" really should be part of the name in any case)
The name we chose (and the implied semantics) will likely have
implications on the handling of Usamas series.
--
Cheers,
David / dhildenb
