The patch titled
Subject: mm/mglru: rework refault detection
has been added to the -mm mm-unstable branch. Its filename is
mm-mglru-rework-refault-detection.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mglru-rework-refault-detection.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: Yu Zhao <yuzhao@xxxxxxxxxx>
Subject: mm/mglru: rework refault detection
Date: Thu, 5 Dec 2024 17:31:25 -0700
With anon and file min_seq being able to move independently, rework
workingset protection as well so that the comparison of refaults between
anon and file is always on an equal footing.
Specifically, make lru_gen_test_recent() return true for refaults
happening within the distance of MAX_NR_GENS. For example, if min_seq of
a type is max_seq-MIN_NR_GENS, refaults from min_seq-1, i.e.,
max_seq-MIN_NR_GENS-1, are also considered recent, since the distance
max_seq-(max_seq-MIN_NR_GENS-1), i.e., MIN_NR_GENS+1 is less than
MAX_NR_GENS.
As an intermediate step to the final optimization, this change by itself
should not have userspace-visiable effects beyond performance.
Link: https://lkml.kernel.org/r/20241206003126.1338283-6-yuzhao@xxxxxxxxxx
Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Reported-by: Kairui Song <kasong@xxxxxxxxxxx>
Closes: https://lore.kernel.org/CAOUHufahuWcKf5f1Sg3emnqX+cODuR=2TQo7T4Gr-QYLujn4RA@xxxxxxxxxxxxxx/
Tested-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: Bharata B Rao <bharata@xxxxxxx>
Cc: David Stevens <stevensd@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/workingset.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
--- a/mm/workingset.c~mm-mglru-rework-refault-detection
+++ a/mm/workingset.c
@@ -260,11 +260,11 @@ static void *lru_gen_eviction(struct fol
* Tests if the shadow entry is for a folio that was recently evicted.
* Fills in @lruvec, @token, @workingset with the values unpacked from shadow.
*/
-static bool lru_gen_test_recent(void *shadow, bool file, struct lruvec **lruvec,
+static bool lru_gen_test_recent(void *shadow, struct lruvec **lruvec,
unsigned long *token, bool *workingset)
{
int memcg_id;
- unsigned long min_seq;
+ unsigned long max_seq;
struct mem_cgroup *memcg;
struct pglist_data *pgdat;
@@ -273,8 +273,10 @@ static bool lru_gen_test_recent(void *sh
memcg = mem_cgroup_from_id(memcg_id);
*lruvec = mem_cgroup_lruvec(memcg, pgdat);
- min_seq = READ_ONCE((*lruvec)->lrugen.min_seq[file]);
- return (*token >> LRU_REFS_WIDTH) == (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH));
+ max_seq = READ_ONCE((*lruvec)->lrugen.max_seq);
+ max_seq &= EVICTION_MASK >> LRU_REFS_WIDTH;
+
+ return abs_diff(max_seq, *token >> LRU_REFS_WIDTH) < MAX_NR_GENS;
}
static void lru_gen_refault(struct folio *folio, void *shadow)
@@ -290,7 +292,7 @@ static void lru_gen_refault(struct folio
rcu_read_lock();
- recent = lru_gen_test_recent(shadow, type, &lruvec, &token, &workingset);
+ recent = lru_gen_test_recent(shadow, &lruvec, &token, &workingset);
if (lruvec != folio_lruvec(folio))
goto unlock;
@@ -331,7 +333,7 @@ static void *lru_gen_eviction(struct fol
return NULL;
}
-static bool lru_gen_test_recent(void *shadow, bool file, struct lruvec **lruvec,
+static bool lru_gen_test_recent(void *shadow, struct lruvec **lruvec,
unsigned long *token, bool *workingset)
{
return false;
@@ -432,8 +434,7 @@ bool workingset_test_recent(void *shadow
bool recent;
rcu_read_lock();
- recent = lru_gen_test_recent(shadow, file, &eviction_lruvec,
- &eviction, workingset);
+ recent = lru_gen_test_recent(shadow, &eviction_lruvec, &eviction, workingset);
rcu_read_unlock();
return recent;
}
_
Patches currently in -mm which might be from yuzhao@xxxxxxxxxx are
mm-mglru-clean-up-workingset.patch
mm-mglru-optimize-deactivation.patch
mm-mglru-rework-aging-feedback.patch
mm-mglru-rework-type-selection.patch
mm-mglru-rework-refault-detection.patch
mm-mglru-rework-workingset-protection.patch
