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mm/mglru: rework refault detection

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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/20241207221522.2250311-6-yuzhao@google.com
Signed-off-by: Yu Zhao <yuzhao@google.com>
Reported-by: Kairui Song <kasong@tencent.com>
Closes: https://lore.kernel.org/CAOUHufahuWcKf5f1Sg3emnqX+cODuR=2TQo7T4Gr-QYLujn4RA@mail.gmail.com/
Tested-by: Kalesh Singh <kaleshsingh@google.com>
Cc: Bharata B Rao <bharata@amd.com>
Cc: David Stevens <stevensd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Yu Zhao 2024-12-07 15:15:21 -07:00 committed by Andrew Morton
parent 51793e247b
commit 1bef50327e
1 changed files with 9 additions and 8 deletions
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17
mm/workingset.c
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@ -260,11 +260,11 @@ static void *lru_gen_eviction(struct folio *folio)
* 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 *shadow, bool file, struct lruvec **lruvec,
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 *folio, void *shadow)
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 folio *folio)
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 file, bool *workingset,
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;
}