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| author | Ruan Shiyang <ruansy.fnst@fujitsu.com> | 2025-07-29 11:51:01 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-09-13 16:54:42 -0700 |
| commit | 337135e6124b6d37d7ef1cd5a6c0b9681938c5ee (patch) | |
| tree | a953d28a85c27bac45d8107790acad60dfdd4c62 /include | |
| parent | mm/mglru: update MG-LRU proactive reclaim statistics only to memcg (diff) | |
| download | linux-337135e6124b6d37d7ef1cd5a6c0b9681938c5ee.tar.gz linux-337135e6124b6d37d7ef1cd5a6c0b9681938c5ee.zip | |
mm: memory-tiering: fix PGPROMOTE_CANDIDATE counting
Goto-san reported confusing pgpromote statistics where the
pgpromote_success count significantly exceeded pgpromote_candidate.
On a system with three nodes (nodes 0-1: DRAM 4GB, node 2: NVDIMM 4GB):
# Enable demotion only
echo 1 > /sys/kernel/mm/numa/demotion_enabled
numactl -m 0-1 memhog -r200 3500M >/dev/null &
pid=$!
sleep 2
numactl memhog -r100 2500M >/dev/null &
sleep 10
kill -9 $pid # terminate the 1st memhog
# Enable promotion
echo 2 > /proc/sys/kernel/numa_balancing
After a few seconds, we observeed `pgpromote_candidate < pgpromote_success`
$ grep -e pgpromote /proc/vmstat
pgpromote_success 2579
pgpromote_candidate 0
In this scenario, after terminating the first memhog, the conditions for
pgdat_free_space_enough() are quickly met, and triggers promotion.
However, these migrated pages are only counted for in PGPROMOTE_SUCCESS,
not in PGPROMOTE_CANDIDATE.
To solve these confusing statistics, introduce PGPROMOTE_CANDIDATE_NRL to
count the missed promotion pages. And also, not counting these pages into
PGPROMOTE_CANDIDATE is to avoid changing the existing algorithm or
performance of the promotion rate limit.
Link: https://lkml.kernel.org/r/20250901090122.124262-1-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/20250729035101.1601407-1-ruansy.fnst@fujitsu.com
Fixes: c6833e10008f ("memory tiering: rate limit NUMA migration throughput")
Co-developed-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Ruan Shiyang <ruansy.fnst@fujitsu.com>
Reported-by: Yasunori Gotou (Fujitsu) <y-goto@fujitsu.com>
Suggested-by: Huang Ying <ying.huang@linux.alibaba.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Huang Ying <ying.huang@linux.alibaba.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mmzone.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 0c5da9141983..9d3ea9085556 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -234,7 +234,21 @@ enum node_stat_item { #endif #ifdef CONFIG_NUMA_BALANCING PGPROMOTE_SUCCESS, /* promote successfully */ - PGPROMOTE_CANDIDATE, /* candidate pages to promote */ + /** + * Candidate pages for promotion based on hint fault latency. This + * counter is used to control the promotion rate and adjust the hot + * threshold. + */ + PGPROMOTE_CANDIDATE, + /** + * Not rate-limited (NRL) candidate pages for those can be promoted + * without considering hot threshold because of enough free pages in + * fast-tier node. These promotions bypass the regular hotness checks + * and do NOT influence the promotion rate-limiter or + * threshold-adjustment logic. + * This is for statistics/monitoring purposes. + */ + PGPROMOTE_CANDIDATE_NRL, #endif /* PGDEMOTE_*: pages demoted */ PGDEMOTE_KSWAPD, |