From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E0EDD24E4A1 for ; Wed, 3 Dec 2025 11:33:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764761594; cv=none; b=DUD5aJvu3qvYKLbsaKfTCPgO6eqCbPteIYUlAig1RY7cHUxjmF/hzdoeXJarqzaJwhs1bmPDxQekBit2hK8qxM8QPC2/uUxsZzwD89Pf+l13bukvIC51pwfZq7bUz5AWvXtXsEida3TbDnV5NtSsS7c9OrHNR75sbwErwof6opk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764761594; c=relaxed/simple; bh=qkitV7n3IcZwSor/OK4RnlgMcECsoeewa2IMTxryTvE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZVO3O0gamEr66zRN3be9t1npWoNFO1Xrchgzvg4CUUPt+wbvVKypjmbN5SD+HNEgeiANq8gV8uA0QhUAea0bdxDh2nluN6hhzseoHfGILBOQGeAu9PVab8zt9m/oqaCCW91EzeOaPHBgqalHV0PUVc0r7bNwi8PJXEhBt68jc58= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nCztgqpj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nCztgqpj" 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 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 -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 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