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Tue, 29 Jul 2025 03:51:07 +0000 (UTC) Received: from localhost.localdomain (unknown [10.167.135.81]) by edo.cn.fujitsu.com (Postfix) with ESMTP id 99DC51A0071; Tue, 29 Jul 2025 11:51:02 +0800 (CST) From: Ruan Shiyang To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, lkp@intel.com, ying.huang@linux.alibaba.com, akpm@linux-foundation.org, y-goto@fujitsu.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, vschneid@redhat.com, Ben Segall , Li Zhijian Subject: [PATCH v1] mm: memory-tiering: Fix PGPROMOTE_CANDIDATE counting Date: Tue, 29 Jul 2025 11:51:01 +0800 Message-ID: <20250729035101.1601407-1-ruansy.fnst@fujitsu.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: AD895100002 X-Stat-Signature: xxhdrdtouc3p1rituctcd413q5fq6ser X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1753761069-850414 X-HE-Meta: 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 SU4y/5qm 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 this confusing statistics, introduce this 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. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Steven Rostedt Cc: Ben Segall Cc: Mel Gorman Cc: Valentin Schneider Reported-by: Yasunori Gotou (Fujitsu) Suggested-by: Huang Ying Signed-off-by: Li Zhijian Signed-off-by: Ruan Shiyang --- Changes since RFC v3: 1. change the naming of new added stat to PGPROMOTE_CANDIDATE_NRL. 2. improve the description of the two stats. --- include/linux/mmzone.h | 16 +++++++++++++++- kernel/sched/fair.c | 5 +++-- mm/vmstat.c | 1 + 3 files changed, 19 insertions(+), 3 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 283913d42d7b..4345996a7d5a 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -230,7 +230,21 @@ 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, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7a14da5396fb..4022c9c1f346 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1940,11 +1940,13 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, struct pglist_data *pgdat; unsigned long rate_limit; unsigned int latency, th, def_th; + long nr = folio_nr_pages(folio); pgdat = NODE_DATA(dst_nid); if (pgdat_free_space_enough(pgdat)) { /* workload changed, reset hot threshold */ pgdat->nbp_threshold = 0; + mod_node_page_state(pgdat, PGPROMOTE_CANDIDATE_NRL, nr); return true; } @@ -1958,8 +1960,7 @@ bool should_numa_migrate_memory(struct task_struct *p, struct folio *folio, if (latency >= th) return false; - return !numa_promotion_rate_limit(pgdat, rate_limit, - folio_nr_pages(folio)); + return !numa_promotion_rate_limit(pgdat, rate_limit, nr); } this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); diff --git a/mm/vmstat.c b/mm/vmstat.c index a78d70ddeacd..bb0d2b330dd5 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1272,6 +1272,7 @@ const char * const vmstat_text[] = { #ifdef CONFIG_NUMA_BALANCING "pgpromote_success", "pgpromote_candidate", + "pgpromote_candidate_nrl", #endif "pgdemote_kswapd", "pgdemote_direct", -- 2.43.0