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Wed, 30 Jul 2025 09:28:47 +0800 From: "Huang, Ying" To: Ruan Shiyang 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, Ben Segall , Li Zhijian Subject: Re: [PATCH v1] mm: memory-tiering: Fix PGPROMOTE_CANDIDATE counting In-Reply-To: <20250729035101.1601407-1-ruansy.fnst@fujitsu.com> (Ruan Shiyang's message of "Tue, 29 Jul 2025 11:51:01 +0800") References: <20250729035101.1601407-1-ruansy.fnst@fujitsu.com> Date: Wed, 30 Jul 2025 09:28:45 +0800 Message-ID: <874iuuzctu.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 7732740013 X-Stat-Signature: qu1t5bufg4545fqtzgwm1q4bj3e654eu X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1753838932-283114 X-HE-Meta: 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 FaDdksqL 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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: Ruan Shiyang writes: > 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 LGTM, feel free to add my Reviewed-by: Huang Ying in the future version. [snip] --- Best Regards, Huang, Ying