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Message-ID: <20241202032823.2741019-5-yuzhao@google.com>
Date: Sun, 1 Dec 2024 20:28:21 -0700
From: Yu Zhao <yuzhao@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Yu Zhao <yuzhao@...gle.com>, David Stevens <stevensd@...omium.org>,
Kalesh Singh <kaleshsingh@...gle.com>
Subject: [PATCH mm-unstable v1 4/6] mm/mglru: rework type selection
With anon and file min_seq being able to move independently, rework
type selection so that it is based on the total refaults from all
tiers of each type. Also allow a type to be selected until that type
reaches MIN_NR_GENS, and therefore abs_diff(min_seq[0],min_seq[1]) now
can be 2 (MAX_NR_GENS-MIN_NR_GENS) instead of 1.
Since some tiers of a selected type can have higher refaults than the
first tier of the other type, use a less larger gain factor 2:3
instead of 1:2, in order for those tiers in the selected type to be
better protected.
As an intermediate step to the final optimization, this change by
itself should not have userspace-visiable effects beyond performance.
Reported-by: David Stevens <stevensd@...omium.org>
Signed-off-by: Yu Zhao <yuzhao@...gle.com>
Tested-by: Kalesh Singh <kaleshsingh@...gle.com>
---
mm/vmscan.c | 82 +++++++++++++++++------------------------------------
1 file changed, 26 insertions(+), 56 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 00a5aff3db42..307ae8b03d0d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3089,15 +3089,20 @@ struct ctrl_pos {
static void read_ctrl_pos(struct lruvec *lruvec, int type, int tier, int gain,
struct ctrl_pos *pos)
{
+ int i;
struct lru_gen_folio *lrugen = &lruvec->lrugen;
int hist = lru_hist_from_seq(lrugen->min_seq[type]);
- pos->refaulted = lrugen->avg_refaulted[type][tier] +
- atomic_long_read(&lrugen->refaulted[hist][type][tier]);
- pos->total = lrugen->avg_total[type][tier] +
- lrugen->protected[hist][type][tier] +
- atomic_long_read(&lrugen->evicted[hist][type][tier]);
+ pos->refaulted = pos->total = 0;
pos->gain = gain;
+
+ for (i = tier % MAX_NR_TIERS; i <= min(tier, MAX_NR_TIERS - 1); i++) {
+ pos->refaulted += lrugen->avg_refaulted[type][i] +
+ atomic_long_read(&lrugen->refaulted[hist][type][i]);
+ pos->total += lrugen->avg_total[type][i] +
+ lrugen->protected[hist][type][i] +
+ atomic_long_read(&lrugen->evicted[hist][type][i]);
+ }
}
static void reset_ctrl_pos(struct lruvec *lruvec, int type, bool carryover)
@@ -4480,13 +4485,13 @@ static int get_tier_idx(struct lruvec *lruvec, int type)
struct ctrl_pos sp, pv;
/*
- * To leave a margin for fluctuations, use a larger gain factor (1:2).
+ * To leave a margin for fluctuations, use a larger gain factor (2:3).
* This value is chosen because any other tier would have at least twice
* as many refaults as the first tier.
*/
- read_ctrl_pos(lruvec, type, 0, 1, &sp);
+ read_ctrl_pos(lruvec, type, 0, 2, &sp);
for (tier = 1; tier < MAX_NR_TIERS; tier++) {
- read_ctrl_pos(lruvec, type, tier, 2, &pv);
+ read_ctrl_pos(lruvec, type, tier, 3, &pv);
if (!positive_ctrl_err(&sp, &pv))
break;
}
@@ -4494,68 +4499,34 @@ static int get_tier_idx(struct lruvec *lruvec, int type)
return tier - 1;
}
-static int get_type_to_scan(struct lruvec *lruvec, int swappiness, int *tier_idx)
+static int get_type_to_scan(struct lruvec *lruvec, int swappiness)
{
- int type, tier;
struct ctrl_pos sp, pv;
- int gain[ANON_AND_FILE] = { swappiness, MAX_SWAPPINESS - swappiness };
+ if (!swappiness)
+ return LRU_GEN_FILE;
+
+ if (swappiness == MAX_SWAPPINESS)
+ return LRU_GEN_ANON;
/*
- * Compare the first tier of anon with that of file to determine which
- * type to scan. Also need to compare other tiers of the selected type
- * with the first tier of the other type to determine the last tier (of
- * the selected type) to evict.
+ * Compare the sum of all tiers of anon with that of file to determine
+ * which type to scan.
*/
- read_ctrl_pos(lruvec, LRU_GEN_ANON, 0, gain[LRU_GEN_ANON], &sp);
- read_ctrl_pos(lruvec, LRU_GEN_FILE, 0, gain[LRU_GEN_FILE], &pv);
- type = positive_ctrl_err(&sp, &pv);
+ read_ctrl_pos(lruvec, LRU_GEN_ANON, MAX_NR_TIERS, swappiness, &sp);
+ read_ctrl_pos(lruvec, LRU_GEN_FILE, MAX_NR_TIERS, MAX_SWAPPINESS - swappiness, &pv);
- read_ctrl_pos(lruvec, !type, 0, gain[!type], &sp);
- for (tier = 1; tier < MAX_NR_TIERS; tier++) {
- read_ctrl_pos(lruvec, type, tier, gain[type], &pv);
- if (!positive_ctrl_err(&sp, &pv))
- break;
- }
-
- *tier_idx = tier - 1;
-
- return type;
+ return positive_ctrl_err(&sp, &pv);
}
static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
int *type_scanned, struct list_head *list)
{
int i;
- int type;
- int tier = -1;
- DEFINE_MIN_SEQ(lruvec);
-
- /*
- * Try to make the obvious choice first, and if anon and file are both
- * available from the same generation,
- * 1. Interpret swappiness 1 as file first and MAX_SWAPPINESS as anon
- * first.
- * 2. If !__GFP_IO, file first since clean pagecache is more likely to
- * exist than clean swapcache.
- */
- if (!swappiness)
- type = LRU_GEN_FILE;
- else if (min_seq[LRU_GEN_ANON] < min_seq[LRU_GEN_FILE])
- type = LRU_GEN_ANON;
- else if (swappiness == 1)
- type = LRU_GEN_FILE;
- else if (swappiness == MAX_SWAPPINESS)
- type = LRU_GEN_ANON;
- else if (!(sc->gfp_mask & __GFP_IO))
- type = LRU_GEN_FILE;
- else
- type = get_type_to_scan(lruvec, swappiness, &tier);
+ int type = get_type_to_scan(lruvec, swappiness);
for_each_evictable_type(i, swappiness) {
int scanned;
-
- if (tier < 0)
- tier = get_tier_idx(lruvec, type);
+ int tier = get_tier_idx(lruvec, type);
*type_scanned = type;
@@ -4564,7 +4535,6 @@ static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int sw
return scanned;
type = !type;
- tier = -1;
}
return 0;
--
2.47.0.338.g60cca15819-goog
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