From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) (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 7F2BE3AB271 for ; Wed, 3 Jun 2026 02:00:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780452056; cv=none; b=A4semyWTQbVgk5FrOXEv2HhxUn2RpJ/eYJsiMLSfrigIn377wXgxf3OKyoTctzqUnwouTDO5IohnoZL5nxLZ0qCxsd7vO/oOL43TuvCzhVMGW4vBZLn0cgVuVEFB0GP1Lyfot9D9sx5O2qLEpC/GiQfaEO3BPMHQ0vNq42BqJGg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780452056; c=relaxed/simple; bh=cvRv8xMtq0WCcjq7Ft9xBpdBJQmg8mtlgWqmwiKIPbc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qnglozntZApEb8FwXbUKC4bw1eQweBHbvY2URQ29NC5G0727S8n7Ko0yCB/CXKusiMmElC1RsRYyml3QSju42IB09vWaJuwRaO7LwSTZEyXlqz8FvHtx19qZ3BWm8gJMTHJa3M7vwRdIAtpTa+OCkYwjBwqI1+sVf3oIhmKWie4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=OpV6w1zh; arc=none smtp.client-ip=95.215.58.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="OpV6w1zh" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780452052; h=from:from: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=LeJhAZRLWtGVTIwFCHuqUJodfl2KhzLTyWve4qcCjP0=; b=OpV6w1zhJuO9Fvzn8HsG5QQIKizSG6UQlTGMYcaaGFMyxQu6EKE+D7en/a3XSllzlZr09c OL45e43afq5M8uzJH+i6A6D/I/7sBvkz4DASrXvWF8YTzQPYljiqO0j2vMSg8whTUhwLAm sdEXdAeJV4ySUtPk/pQSFbGcLsXdX4g= Date: Wed, 3 Jun 2026 10:00:33 +0800 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH 1/1] mm/thp: clear deferred split shrinker bits when queues drain Content-Language: en-US To: Andrew Morton Cc: david@kernel.org, ljs@kernel.org, shakeel.butt@linux.dev, mhocko@kernel.org, david@fromorbit.com, roman.gushchin@linux.dev, muchun.song@linux.dev, qi.zheng@linux.dev, yosry.ahmed@linux.dev, ziy@nvidia.com, liam@infradead.org, usama.arif@linux.dev, kas@kernel.org, vbabka@kernel.org, ryncsn@gmail.com, zaslonko@linux.ibm.com, gor@linux.ibm.com, wangkefeng.wang@huawei.com, baolin.wang@linux.alibaba.com, baohua@kernel.org, dev.jain@arm.com, npache@redhat.com, ryan.roberts@arm.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner References: <20260602043453.67597-1-lance.yang@linux.dev> <20260602133706.d737a82858d1cf89870521b1@linux-foundation.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20260602133706.d737a82858d1cf89870521b1@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2026/6/3 04:37, Andrew Morton wrote: > On Tue, 2 Jun 2026 12:34:53 +0800 Lance Yang wrote: > >> From: Lance Yang >> >> deferred_split_count() returns the raw list_lru count. When the per-memcg, >> per-node list is empty, that count is 0. >> >> That skips scanning, but it does not tell memcg reclaim that the shrinker >> is empty. shrink_slab_memcg() only clears the memcg shrinker bit when the >> count callback reports SHRINK_EMPTY. >> >> Return SHRINK_EMPTY for an empty deferred split list, so the bit can be >> cleared once the queue has drained. >> >> Signed-off-by: Lance Yang >> --- >> mm/huge_memory.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 72f6caf0fec6..62d598290c3b 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -4397,7 +4397,10 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped) >> static unsigned long deferred_split_count(struct shrinker *shrink, >> struct shrink_control *sc) >> { >> - return list_lru_shrink_count(&deferred_split_lru, sc); >> + unsigned long count; >> + >> + count = list_lru_shrink_count(&deferred_split_lru, sc); >> + return count ?: SHRINK_EMPTY; >> } >> >> static bool thp_underused(struct folio *folio) > > Should this be handled as a fix against hannes's "mm: switch deferred > split shrinker to list_lru"? Hmm ... I noticed this while looking at Johannes' work, but the behavior is older than that ... We also discussed the Fixes tag earlier[1] and decided to leave it out. There is no missed reclaim, only some extra reclaim work :) [1] https://lore.kernel.org/linux-mm/63797977-1c18-4885-8099-f5c21c80da39@linux.dev/ Cheers, Lance