The quilt patch titled
Subject: mm, lru_gen: try to prefetch next page when scanning LRU
has been removed from the -mm tree. Its filename was
mm-lru_gen-try-to-prefetch-next-page-when-canning-lru.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
From: Kairui Song <kasong@xxxxxxxxxxx>
Subject: mm, lru_gen: try to prefetch next page when scanning LRU
Date: Fri, 12 Jan 2024 02:33:21 +0800
Prefetch for inactive/active LRU have been long exiting, apply the same
optimization for MGLRU.
Ramdisk based swap test in a 4G memcg on a EPYC 7K62 with:
memcached -u nobody -m 16384 -s /tmp/memcached.socket \
-a 0766 -t 16 -B binary &
memtier_benchmark -S /tmp/memcached.socket \
-P memcache_binary -n allkeys \
--key-minimum=1 --key-maximum=16000000 -d 1024 \
--ratio=1:0 --key-pattern=P:P -c 2 -t 16 --pipeline 8 -x 6
Average result of 18 test runs:
Before: 44017.78 Ops/sec
After patch 1-3: 44890.50 Ops/sec (+1.8%)
Ramdisk fio test in a 4G memcg on a EPYC 7K62 with:
fio -name=mglru --numjobs=16 --directory=/mnt --size=960m \
--buffered=1 --ioengine=io_uring --iodepth=128 \
--iodepth_batch_submit=32 --iodepth_batch_complete=32 \
--rw=randread --random_distribution=zipf:0.5 --norandommap \
--time_based --ramp_time=1m --runtime=5m --group_reporting
Before this patch:
bw ( MiB/s): min= 7644, max= 9293, per=100.00%, avg=8777.77, stdev=16.59, samples=9568
iops : min=1956954, max=2379053, avg=2247108.51, stdev=4247.22, samples=9568
After this patch (+7.5%):
bw ( MiB/s): min= 8462, max= 9902, per=100.00%, avg=9444.77, stdev=16.43, samples=9568
iops : min=2166433, max=2535135, avg=2417858.23, stdev=4205.15, samples=9568
Prefetch is highly related to timing and architecture so it may only help in
certain cases, some extra test showed at least no regression here for
the series:
Ramdisk memtier test above in a 8G memcg on an Intel i7-9700:
memtier_benchmark -S /tmp/memcached.socket \
-P memcache_binary -n allkeys --key-minimum=1 \
--key-maximum=36000000 --key-pattern=P:P -c 1 -t 12 \
--ratio 1:0 --pipeline 8 -d 1024 -x 4
Average result of 12 test runs:
Before: 61241.96 Ops/sec
After patch 1-3: 61268.53 Ops/sec (+0.0%)
Link: https://lkml.kernel.org/r/20240111183321.19984-4-ryncsn@xxxxxxxxx
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Chris Li <chrisl@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
--- a/mm/vmscan.c~mm-lru_gen-try-to-prefetch-next-page-when-canning-lru
+++ a/mm/vmscan.c
@@ -3773,10 +3773,12 @@ static bool inc_min_seq(struct lruvec *l
VM_WARN_ON_ONCE_FOLIO(folio_is_file_lru(folio) != type, folio);
VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
- if (unlikely(list_is_first(&folio->lru, head)))
+ if (unlikely(list_is_first(&folio->lru, head))) {
prev = NULL;
- else
+ } else {
prev = lru_to_folio(&folio->lru);
+ prefetchw(&prev->flags);
+ }
new_gen = folio_inc_gen(lruvec, folio, false, &batch);
lru_gen_try_inc_bulk(lrugen, folio, bulk_gen, new_gen, type, zone, &batch);
@@ -4452,10 +4454,12 @@ static int scan_folios(struct lruvec *lr
VM_WARN_ON_ONCE_FOLIO(folio_zonenum(folio) != zone, folio);
scanned += delta;
- if (unlikely(list_is_first(&folio->lru, head)))
+ if (unlikely(list_is_first(&folio->lru, head))) {
prev = NULL;
- else
+ } else {
prev = lru_to_folio(&folio->lru);
+ prefetchw(&prev->flags);
+ }
if (sort_folio(lruvec, folio, sc, tier, bulk_gen, &batch))
sorted += delta;
_
Patches currently in -mm which might be from kasong@xxxxxxxxxxx are
