[PATCH v8 09/14] mm: multi-gen LRU: optimize multiple memcgs
Yu Zhao
yuzhao at google.com
Tue Mar 8 15:47:19 PST 2022
When multiple memcgs are available, it is possible to make better
choices based on generations and tiers and therefore improve the
overall performance under global memory pressure. This patch adds a
rudimentary optimization to select memcgs that can drop single-use
unmapped clean pages first. Doing so reduces the chance of going into
the aging path or swapping. These two operations can be costly.
A typical example that benefits from this optimization is a server
running mixed types of workloads, e.g., heavy anon workload in one
memcg and heavy buffered I/O workload in the other.
Though this optimization can be applied to both kswapd and direct
reclaim, it is only added to kswapd to keep the patchset manageable.
Later improvements will cover the direct reclaim path.
Server benchmark results:
Mixed workloads:
fio (buffered I/O): -[28, 30]%
IOPS BW
patch1-7: 3117k 11.9GiB/s
patch1-8: 2217k 8661MiB/s
memcached (anon): +[247, 251]%
Ops/sec KB/sec
patch1-7: 563772.35 21900.01
patch1-8: 1968343.76 76461.24
Mixed workloads:
fio (buffered I/O): -[4, 6]%
IOPS BW
5.17-rc2: 2338k 9133MiB/s
patch1-8: 2217k 8661MiB/s
memcached (anon): +[524, 530]%
Ops/sec KB/sec
5.17-rc2: 313821.65 12190.55
patch1-8: 1968343.76 76461.24
Configurations:
(changes since patch 5)
cat mixed.sh
modprobe brd rd_nr=2 rd_size=56623104
swapoff -a
mkswap /dev/ram0
swapon /dev/ram0
mkfs.ext4 /dev/ram1
mount -t ext4 /dev/ram1 /mnt
memtier_benchmark -S /var/run/memcached/memcached.sock \
-P memcache_binary -n allkeys --key-minimum=1 \
--key-maximum=50000000 --key-pattern=P:P -c 1 -t 36 \
--ratio 1:0 --pipeline 8 -d 2000
fio -name=mglru --numjobs=36 --directory=/mnt --size=1408m \
--buffered=1 --ioengine=io_uring --iodepth=128 \
--iodepth_batch_submit=32 --iodepth_batch_complete=32 \
--rw=randread --random_distribution=random --norandommap \
--time_based --ramp_time=10m --runtime=90m --group_reporting &
pid=$!
sleep 200
memtier_benchmark -S /var/run/memcached/memcached.sock \
-P memcache_binary -n allkeys --key-minimum=1 \
--key-maximum=50000000 --key-pattern=R:R -c 1 -t 36 \
--ratio 0:1 --pipeline 8 --randomize --distinct-client-seed
kill -INT $pid
wait
Client benchmark results:
no change (CONFIG_MEMCG=n)
Signed-off-by: Yu Zhao <yuzhao at google.com>
Acked-by: Brian Geffon <bgeffon at google.com>
Acked-by: Jan Alexander Steffens (heftig) <heftig at archlinux.org>
Acked-by: Oleksandr Natalenko <oleksandr at natalenko.name>
Acked-by: Steven Barrett <steven at liquorix.net>
Acked-by: Suleiman Souhlal <suleiman at google.com>
Tested-by: Daniel Byrne <djbyrne at mtu.edu>
Tested-by: Donald Carr <d at chaos-reins.com>
Tested-by: Holger Hoffstätte <holger at applied-asynchrony.com>
Tested-by: Konstantin Kharlamov <Hi-Angel at yandex.ru>
Tested-by: Shuang Zhai <szhai2 at cs.rochester.edu>
Tested-by: Sofia Trinh <sofia.trinh at edi.works>
Tested-by: Vaibhav Jain <vaibhav at linux.ibm.com>
---
mm/vmscan.c | 45 +++++++++++++++++++++++++++++++++++++++++----
1 file changed, 41 insertions(+), 4 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 67dc4190e790..7375c9dae08f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -127,6 +127,13 @@ struct scan_control {
/* Always discard instead of demoting to lower tier memory */
unsigned int no_demotion:1;
+#ifdef CONFIG_LRU_GEN
+ /* help make better choices when multiple memcgs are available */
+ unsigned int memcgs_need_aging:1;
+ unsigned int memcgs_need_swapping:1;
+ unsigned int memcgs_avoid_swapping:1;
+#endif
+
/* Allocation order */
s8 order;
@@ -4348,6 +4355,22 @@ static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
VM_BUG_ON(!current_is_kswapd());
+ /*
+ * To reduce the chance of going into the aging path or swapping, which
+ * can be costly, optimistically skip them unless their corresponding
+ * flags were cleared in the eviction path. This improves the overall
+ * performance when multiple memcgs are available.
+ */
+ if (!sc->memcgs_need_aging) {
+ sc->memcgs_need_aging = true;
+ sc->memcgs_avoid_swapping = !sc->memcgs_need_swapping;
+ sc->memcgs_need_swapping = true;
+ return;
+ }
+
+ sc->memcgs_need_swapping = true;
+ sc->memcgs_avoid_swapping = true;
+
current->reclaim_state->mm_walk = &pgdat->mm_walk;
memcg = mem_cgroup_iter(NULL, NULL, NULL);
@@ -4750,7 +4773,8 @@ static int isolate_folios(struct lruvec *lruvec, struct scan_control *sc, int sw
return scanned;
}
-static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness)
+static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swappiness,
+ bool *swapped)
{
int type;
int scanned;
@@ -4816,6 +4840,9 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
sc->nr_reclaimed += reclaimed;
+ if (type == LRU_GEN_ANON && swapped)
+ *swapped = true;
+
return scanned;
}
@@ -4844,8 +4871,10 @@ static long get_nr_to_scan(struct lruvec *lruvec, struct scan_control *sc, bool
if (!nr_to_scan)
return 0;
- if (!need_aging)
+ if (!need_aging) {
+ sc->memcgs_need_aging = false;
return nr_to_scan;
+ }
/* leave the work to lru_gen_age_node() */
if (current_is_kswapd())
@@ -4867,6 +4896,8 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
{
struct blk_plug plug;
long scanned = 0;
+ bool swapped = false;
+ unsigned long reclaimed = sc->nr_reclaimed;
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
lru_add_drain();
@@ -4892,13 +4923,19 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
if (!nr_to_scan)
break;
- delta = evict_folios(lruvec, sc, swappiness);
+ delta = evict_folios(lruvec, sc, swappiness, &swapped);
if (!delta)
break;
+ if (sc->memcgs_avoid_swapping && swappiness < 200 && swapped)
+ break;
+
scanned += delta;
- if (scanned >= nr_to_scan)
+ if (scanned >= nr_to_scan) {
+ if (!swapped && sc->nr_reclaimed - reclaimed >= MIN_LRU_BATCH)
+ sc->memcgs_need_swapping = false;
break;
+ }
cond_resched();
}
--
2.35.1.616.g0bdcbb4464-goog
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