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c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1764809193; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eOj2tIJIgnV8eTwawuGz++SgJKddYFUsPXpSIfwlY6M=; b=gHf3mMpx1FEPlLUtnSjwvNFAo3SnVfh39dcFScqYnX3PvsVkYMilJlyTTqd0vRG8pGI//a Mq5jE1MAaeL/jRUFVaxDNq2NWM+YGZVKqSOOCbVNe2i71pZzv3tOZGV+BaVUN0Cib4DvsG ecb4E3S5sztRKSS7OH5w2QT9iCxWgV8= Received: from mail.maildlp.com (unknown [172.19.163.216]) by dggsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4dMG5D1HsRzKHLyn for ; Thu, 4 Dec 2025 08:45:36 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.75]) by mail.maildlp.com (Postfix) with ESMTP id 55FD31A14E1 for ; Thu, 4 Dec 2025 08:46:26 +0800 (CST) Received: from [10.67.111.176] (unknown [10.67.111.176]) by APP2 (Coremail) with SMTP id Syh0CgAH5k_g2TBp52sQAg--.43129S2; Thu, 04 Dec 2025 08:46:26 +0800 (CST) Message-ID: <75ce1699-2c5a-4aab-acee-cca5c6a1e37c@huaweicloud.com> Date: Thu, 4 Dec 2025 08:46:24 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next] mm: vmscan: correct nr_requested tracing in scan_folios To: "David Hildenbrand (Red Hat)" , 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> <98cbf348-ff21-4c90-af32-b8009c34e5fd@kernel.org> Content-Language: en-US From: Chen Ridong In-Reply-To: <98cbf348-ff21-4c90-af32-b8009c34e5fd@kernel.org> Content-Type: text/plain; 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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. > I prefer tracing nr_to_scan, as it reflects the original target number of pages we intended to scan. Even if nr_to_scan exceeds MAX_LRU_BATCH, we can still deduce that it was effectively capped by examining the actual scanned, skipped, or isolated counts. However, if we trace min(nr_to_scan, MAX_LRU_BATCH) instead, we would lose visibility into what the original nr_to_scan value was. -- Best regards, Ridong