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Tue, 22 Jul 2025 14:16:55 +0000 (UTC) Received: from localhost.localdomain (unknown [10.167.135.81]) by edo.cn.fujitsu.com (Postfix) with ESMTP id 2C2F11A0071; Tue, 22 Jul 2025 22:16:51 +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 , Ben Segall Subject: [PATCH RFC v3] mm: memory-tiering: Fix PGPROMOTE_CANDIDATE counting Date: Tue, 22 Jul 2025 22:16:50 +0800 Message-ID: <20250722141650.1821721-1-ruansy.fnst@fujitsu.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 0E55D4001A X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: 33ghqdkk15bymrxrybto1r48ccj7gjkj X-HE-Tag: 1753193817-260147 X-HE-Meta: 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 RRb2MX5J xUTHEQR/LiAF7uh+0Pkk/lLj/aJ5/BzKg1y/eXDJGMG7f8mjxBIbAtD5epg== 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: From: Li Zhijian === Changes since v2: 1. According to Huang's suggestion, add a new stat to not count these pages into PGPROMOTE_CANDIDATE, to avoid changing the rate limit mechanism. === 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_NOLIMIT 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. Perhaps PGPROMOTE_CANDIDATE_NOLIMIT is not well named, please comment if you have a better idea. Cc: Huang Ying 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) Signed-off-by: Li Zhijian Signed-off-by: Ruan Shiyang --- include/linux/mmzone.h | 2 ++ kernel/sched/fair.c | 6 ++++-- mm/vmstat.c | 1 + 3 files changed, 7 insertions(+), 2 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 283913d42d7b..6216e2eecf3b 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -231,6 +231,8 @@ enum node_stat_item { #ifdef CONFIG_NUMA_BALANCING PGPROMOTE_SUCCESS, /* promote successfully */ PGPROMOTE_CANDIDATE, /* candidate pages to promote */ + PGPROMOTE_CANDIDATE_NOLIMIT, /* candidate pages without considering + * hot threshold */ #endif /* PGDEMOTE_*: pages demoted */ PGDEMOTE_KSWAPD, diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7a14da5396fb..12dac3519c49 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1940,11 +1940,14 @@ 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_NOLIMIT, + nr); return true; } @@ -1958,8 +1961,7 @@ 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..ca44a2dd5497 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_nolimit", #endif "pgdemote_kswapd", "pgdemote_direct", -- 2.43.0