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imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=nCztgqpj; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1764761594; a=rsa-sha256; cv=none; b=JxhbDMoc12XeKw42JEmnKBPlFLAAIt3gjrYuPVi0vc2NeWKTKmmh0lIUbUsh2BYm56ilfc NJ1NRiSIBDs74u6ZFcTjJ92x/IwVl3w7vVzluU4yeadaOF8B13HStv8KcTdIO2EVe+pOlF PYQXTErClMMfqbtbWXDwcGGoXc57uio= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id C1E9560172; Wed, 3 Dec 2025 11:33:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 860C1C4CEFB; Wed, 3 Dec 2025 11:33:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764761593; bh=qkitV7n3IcZwSor/OK4RnlgMcECsoeewa2IMTxryTvE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=nCztgqpjFPJOQS/0o8qWY8aAUUH6aR+l4w2XdhKpQ5sKYB7We7KzslTZ+3nbQyule FgDl4wiQ/l89eqUEeqViaSnvhZJV7idUHiDDE969P5md22Jl+yBQO+lkRAZ+/Cw0Y3 sR+TUxQGQaqy2kaPcwwCb0dKgXkr+ldhiFlZ2qDQX09p6Tegf+fDUQ0gyzAny1HoTn IPrOjvMqN+g3Kx9U/6hWKIE5mDFL4KUIlwz98MKWCZeQUlllBYkQgu3n4fGE23flzD a+EHtyqOklKWqSyxCtoVsoNTx3TS9ofHegddCyTO7Jj4FV6oLoP65kLXFpvm+tOOcD vijTV0BaEbnvQ== Message-ID: <98cbf348-ff21-4c90-af32-b8009c34e5fd@kernel.org> Date: Wed, 3 Dec 2025 12:33:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next] mm: vmscan: correct nr_requested tracing in scan_folios To: Chen Ridong , akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, yuzhao@google.com, jaewon31.kim@samsung.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, lujialin4@huawei.com, chenridong@huawei.com References: <20251203094002.1745458-1-chenridong@huaweicloud.com> From: "David Hildenbrand (Red Hat)" Content-Language: en-US In-Reply-To: <20251203094002.1745458-1-chenridong@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 820581C0014 X-Stat-Signature: z3gmc5xa7ix6nd4weqy96jt9hbj716jz X-Rspam-User: X-HE-Tag: 1764761594-79978 X-HE-Meta: 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 ZGtGAHH2 qj183hRGi9oPQGP0P4QPZanoD5vF0DFJnWmXrp5Y2qCw0SdNmeOu+IMl8O2IZbuXdmzdUGEQWRFqpm55rg3UxJabaagmRPz6LCP59EWUSnojllibERqdjyrzJG8eTyO6CPX43D3+4TyviY35yu6vc0y/ZI4qcps1ol3Y/WoxkX+jqUO2w6J+zdZj30gOPD7cn4ljjcIYv8uYJUBgGEciHH22x+8tQ4D5AhIkgj1g0XYkGD+/BwWS5gsJ7eFVUHpu0TMMyYecrYsXShqAwMTj6DBgT18qqXVsA/LiMH7v/w42/KidLoEyN6phpyPcInd8QAa7DDNEPZRwGR/U= 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: On 12/3/25 10:40, Chen Ridong wrote: > From: Chen Ridong > > When enabling vmscan tracing, it is observed that nr_requested is always > 4096, which is confusing. > > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > mm_vmscan_lru_isolate: classzone=3 order=0 nr_requested=4096 ... > > This is because it prints MAX_LRU_BATCH, which is meaningless as it's a > constant. To fix this, modify it to print nr_to_scan as isolate_lru_folios > does. > > Fixes: 8c2214fc9a47 ("mm: multi-gen LRU: reuse some legacy trace events") > Signed-off-by: Chen Ridong > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index fddd168a9737..8cfafd50a7a8 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -4601,7 +4601,7 @@ static int scan_folios(unsigned long nr_to_scan, struct lruvec *lruvec, > count_memcg_events(memcg, item, isolated); > count_memcg_events(memcg, PGREFILL, sorted); > __count_vm_events(PGSCAN_ANON + type, isolated); > - trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH, > + trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan, > scanned, skipped, isolated, We do that in isolate_lru_folios(). Given that we do int remaining = min(nr_to_scan, MAX_LRU_BATCH); and effectively cap it, I wonder if we would want to trace that capped valued instead of MAX_LRU_BATCH. -- Cheers David