The patch titled
Subject: mm: add sysfs entry to disable splitting underutilized THPs
has been added to the -mm mm-unstable branch. Its filename is
mm-add-sysfs-entry-to-disable-splitting-underutilized-thps.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-add-sysfs-entry-to-disable-splitting-underutilized-thps.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Usama Arif <usamaarif642@xxxxxxxxx>
Subject: mm: add sysfs entry to disable splitting underutilized THPs
Date: Tue, 13 Aug 2024 13:02:49 +0100
If disabled, THPs faulted in or collapsed will not be added to
_deferred_list, and therefore won't be considered for splitting under
memory pressure if underutilized.
Link: https://lkml.kernel.org/r/20240813120328.1275952-7-usamaarif642@xxxxxxxxx
Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
Cc: Alexander Zhu <alexlzhu@xxxxxx>
Cc: Barry Song <baohua@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Domenico Cerasuolo <cerasuolodomenico@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Cc: Shuang Zhai <zhais@xxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
--- a/mm/huge_memory.c~mm-add-sysfs-entry-to-disable-splitting-underutilized-thps
+++ a/mm/huge_memory.c
@@ -74,6 +74,7 @@ static unsigned long deferred_split_coun
struct shrink_control *sc);
static unsigned long deferred_split_scan(struct shrinker *shrink,
struct shrink_control *sc);
+static bool split_underutilized_thp = true;
static atomic_t huge_zero_refcount;
struct folio *huge_zero_folio __read_mostly;
@@ -439,6 +440,27 @@ static ssize_t hpage_pmd_size_show(struc
static struct kobj_attribute hpage_pmd_size_attr =
__ATTR_RO(hpage_pmd_size);
+static ssize_t split_underutilized_thp_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%d\n", split_underutilized_thp);
+}
+
+static ssize_t split_underutilized_thp_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int err = kstrtobool(buf, &split_underutilized_thp);
+
+ if (err < 0)
+ return err;
+
+ return count;
+}
+
+static struct kobj_attribute split_underutilized_thp_attr = __ATTR(
+ thp_low_util_shrinker, 0644, split_underutilized_thp_show, split_underutilized_thp_store);
+
static struct attribute *hugepage_attr[] = {
&enabled_attr.attr,
&defrag_attr.attr,
@@ -447,6 +469,7 @@ static struct attribute *hugepage_attr[]
#ifdef CONFIG_SHMEM
&shmem_enabled_attr.attr,
#endif
+ &split_underutilized_thp_attr.attr,
NULL,
};
@@ -3468,6 +3491,9 @@ void deferred_split_folio(struct folio *
if (folio_order(folio) <= 1)
return;
+ if (!partially_mapped && !split_underutilized_thp)
+ return;
+
/*
* The try_to_unmap() in page reclaim path might reach here too,
* this may cause a race condition to corrupt deferred split queue.
_
Patches currently in -mm which might be from usamaarif642@xxxxxxxxx are
mm-introduce-a-pageflag-for-partially-mapped-folios.patch
mm-split-underutilized-thps.patch
mm-add-sysfs-entry-to-disable-splitting-underutilized-thps.patch
