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Thu, 24 Jul 2025 02:39:45 +0000 (UTC) Received: from [192.168.22.105] (unknown [10.167.135.81]) by edo.cn.fujitsu.com (Postfix) with ESMTP id C9EC11A000B; Thu, 24 Jul 2025 10:39:40 +0800 (CST) Message-ID: <85d83be2-02f8-4ef6-91c7-ff920e47d834@fujitsu.com> Date: Thu, 24 Jul 2025 10:39:40 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3] mm: memory-tiering: Fix PGPROMOTE_CANDIDATE counting To: "Huang, Ying" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, lkp@intel.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 References: <20250722141650.1821721-1-ruansy.fnst@fujitsu.com> <87cy9r38ny.fsf@DESKTOP-5N7EMDA> From: Shiyang Ruan In-Reply-To: <87cy9r38ny.fsf@DESKTOP-5N7EMDA> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A5097100009 X-Stat-Signature: qadyw14yeire5eafyubzabyndq7dzeyu X-Rspam-User: X-HE-Tag: 1753324787-846220 X-HE-Meta: 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 2PyXU+4u 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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: 在 2025/7/23 11:09, Huang, Ying 写道: > Ruan Shiyang writes: > >> 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. >> === > > This isn't the popular place for changelog, please refer to other patch > email. OK. I'll move this part down below.> >> 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. > > Yes. Naming is hard. I guess that the name comes from the promotion > that isn't rate limited. I have asked Deepseek that what is the good > abbreviation for "not rate limited". Its answer is "NRL". I don't know > whether it's good. However, "NOT_RATE_LIMITED" appears too long. "NRL" Sounds good to me. I'm thinking another one: since it's not rate limited, it could be migrated quickly/fast. How about PGPROMOTE_CANDIDATE_FAST? > >> >> > > The empty line is unnecessary. OK.> >> Cc: Huang Ying > > Suggested-by: Huang Ying OK. -- Thanks, Ruan. > >> 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", > > --- > Best Regards, > Huang, Ying