From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from esa10.hc1455-7.c3s2.iphmx.com (esa10.hc1455-7.c3s2.iphmx.com [139.138.36.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0960413A41F for ; Thu, 24 Jul 2025 02:39:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=139.138.36.225 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753324798; cv=none; b=BdosNrmXoYJb8R4dOHQS3nIwIn/shGHK0lnpb4IUjHYwf3yHU8y2dlrDnBIOdLohdolXsmE/4vNt9xzzd+3xWagbOsOX2uDN0dcnsjPVs5Kbb53y0U3oArZ8Dgzd26rInM6CSGce7vpryXGOwX/V3cIW9mtowt/xL7vqXkf3kQs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753324798; c=relaxed/simple; bh=uPlh/YWX4gV2j+/e8PX8tFDcfpt6QXFzRYCQvBZYddQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XaOkURKRWps9V0YRPQHfymy6sywh1xFP76fz60FXvM/N1M8hSMcJoXQopSFeQS9mXo9REyer2C+3YPP24b4AihLvIbNGLIP+0z/QWWEb85o8uFTJPmUDOJA/mYFJTy316le9B+5V7XJ/t1lbHWHE3hc7bOK1EtKxwwPGuomsKkk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=fujitsu.com; spf=pass smtp.mailfrom=fujitsu.com; dkim=pass (2048-bit key) header.d=fujitsu.com header.i=@fujitsu.com header.b=hnTrK6aU; arc=none smtp.client-ip=139.138.36.225 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=fujitsu.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fujitsu.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=fujitsu.com header.i=@fujitsu.com header.b="hnTrK6aU" DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=fujitsu.com; i=@fujitsu.com; q=dns/txt; s=fj2; t=1753324796; x=1784860796; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=uPlh/YWX4gV2j+/e8PX8tFDcfpt6QXFzRYCQvBZYddQ=; b=hnTrK6aUt/a+R5BeX06rR8iWkdNRxqLEdl0WMfKn9l9BkXHzgnbEq/RS O2aJBuGSvTzAetcYK5gGhlhnUmbpoTa6c2qIxrxnLLBgesKkFnHR9ThrC LqzDaNIkSjsV3WRVYlh+5l3+VAI9kjs39IreNUaZ7Jlm0w87vx5/BFzKw pZfohus0KYaE6bTFo76CZiKYu019VQ65Cq02QPQ53PImMj7TRsYk6ZzrD fFxxh5pRvOCdiW9q93M9m2xXGLHnRhxU0ywTrEhgMJO4CF7T22q4sgDWi lx34N1CVWmLVXWHLnsk0qBbF3lRpiyAZlzN9kVPS5loTLU8fkObe4cFvT w==; X-CSE-ConnectionGUID: P2LuWKqKRvihFbcbtRInRg== X-CSE-MsgGUID: bpaWRR2RTNOHeBwBjZTLYw== X-IronPort-AV: E=McAfee;i="6800,10657,11501"; a="194633424" X-IronPort-AV: E=Sophos;i="6.16,336,1744038000"; d="scan'208";a="194633424" Received: from unknown (HELO az2nlsmgr4.o.css.fujitsu.com) ([20.61.8.234]) by esa10.hc1455-7.c3s2.iphmx.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jul 2025 11:39:51 +0900 Received: from az2nlsmgm4.fujitsu.com (unknown [10.150.26.204]) (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 az2nlsmgr4.o.css.fujitsu.com (Postfix) with ESMTPS id 327B142A307 for ; Thu, 24 Jul 2025 02:39:51 +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 az2nlsmgm4.fujitsu.com (Postfix) with ESMTPS id 95E301000380 for ; Thu, 24 Jul 2025 02:39:50 +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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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