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Mon, 1 Sep 2025 02:05:44 +0000 (UTC) Received: from edo.cn.fujitsu.com (edo.cn.fujitsu.com [10.167.33.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by az2nlsmom4.fujitsu.com (Postfix) with ESMTPS id 2D4052000222; Mon, 1 Sep 2025 02:05:42 +0000 (UTC) Received: from localhost.localdomain (unknown [10.167.135.81]) by edo.cn.fujitsu.com (Postfix) with ESMTP id 9794A1A0074; Mon, 1 Sep 2025 10:05:38 +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, Li Zhijian , Vlastimil Babka , Ben Segall , stable@vger.kernel.org Subject: [PATCH v2] mm: memory-tiering: fix PGPROMOTE_CANDIDATE counting Date: Mon, 1 Sep 2025 10:05:38 +0800 Message-ID: <20250901020538.3960468-1-ruansy.fnst@fujitsu.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250729035101.1601407-1-ruansy.fnst@fujitsu.com> References: <20250729035101.1601407-1-ruansy.fnst@fujitsu.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: ntq15hzf4t8gnywhripw8sctjudjb71z X-Rspam-User: X-Rspamd-Queue-Id: 6C62018000A X-Rspamd-Server: rspam01 X-HE-Tag: 1756692346-842621 X-HE-Meta: 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 ph+poJib 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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 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/20250729035101.1601407-1-ruansy.fnst@fujitsu.com Co-developed-by: Li Zhijian Signed-off-by: Ruan Shiyang Reported-by: Yasunori Gotou (Fujitsu) Suggested-by: Huang Ying Acked-by: Vlastimil Babka 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 Cc: Signed-off-by: Andrew Morton --- Changes since v1: 1. change Li Zhijian from 'Signed-off-by' to 'Co-developed-by' per Vlastimil. 2. add Acked-by: Vlastimil Babka --- 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 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, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b173a059315c..82c8d804c54c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1923,11 +1923,13 @@ 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; } @@ -1941,8 +1943,7 @@ 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 71cd1ceba191..e74f0b2a1021 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1280,6 +1280,7 @@ const char * const vmstat_text[] = { #ifdef CONFIG_NUMA_BALANCING [I(PGPROMOTE_SUCCESS)] = "pgpromote_success", [I(PGPROMOTE_CANDIDATE)] = "pgpromote_candidate", + [I(PGPROMOTE_CANDIDATE_NRL)] = "pgpromote_candidate_nrl", #endif [I(PGDEMOTE_KSWAPD)] = "pgdemote_kswapd", [I(PGDEMOTE_DIRECT)] = "pgdemote_direct", -- 2.43.0