From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E9FA1219A8A; Tue, 2 Jun 2026 12:11:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780402284; cv=none; b=rRHy2vZ4xZHPotiOj2u80/zMQObFWy7K1lDOHmfK5PInMgxJFOhM/JJouIZ8RskaYFAEsjPlxKGZQ3T/T+2d5M/KdtpBpgIYS2GoOJN6q9FGzCZrMagfYafiLugU3qSdcq1ZKytwRXhzz0nYBvmfRXRnwoYuy/8bwQRQAJHenZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780402284; c=relaxed/simple; bh=RRvUvUS6VJb66nCx/5JOfbA912nl9DHVzkMWgOCNjWk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jVIcOIVCKdbWZloGPIMcBf2+d8/5VDI3O0qldMMj6pYs9jXBIAzG8Vma3Nxd+/75lEBLYl63J4sQ+Vex+4yYEPXTQwc5KvmVDxpNI//jFQGhY8F4wqDFbk0EIO1yiz1LX7sHj9vAbCaf11T4WX18yidLK51L/38YQYrJdnQlKbA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QEIm92HT; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QEIm92HT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3823A1F00893; Tue, 2 Jun 2026 12:11:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780402283; bh=DQxf22WiuMhWZeadAm3Nzhuu9AKEU1pYXtTdOyKS3Iw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=QEIm92HTankRnWAoOl3s0CVEUmiBcSwE+/rA1U8WIrhMSiJa7A9uYtSOOyQAxllAH 23/lI509xvayAf1RjWg9a9ANlH/YK3W07wl/JbQSHydjl4VbQ/HtPks+hfQrHcil/c l9vbYojjqtvD52h48V3D10AuKdx+O0PJx8plH3XSkRUxxPQ8B0q0Ut4H49rBKcfE5U GMvMyMDsSBvfTdglAESpRIp0W8hwci1y99wuEWIBbVLOm8prwITIDgmnw9sVxkuW3n ilrWuLXZMOWI6GyVaBEai63svLfEXVbSWeGMd6CX5R+Uvy1cCQuSoRU9yE0Eq5x7zR k35q+gYWDsBGQ== Message-ID: <716c7351-2641-4317-8675-e07a16a1efe2@kernel.org> Date: Tue, 2 Jun 2026 14:11:16 +0200 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] mm/thp: clear deferred split shrinker bits when queues drain To: Lance Yang , akpm@linux-foundation.org, hannes@cmpxchg.org Cc: 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 References: <20260602043453.67597-1-lance.yang@linux.dev> <1dce1561-b42a-4322-a99f-89eba1e7c227@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/2/26 06:38, Lance Yang wrote: > Sorry, I missed Johannes in Cc ... > > On 2026/6/2 12:34, 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. What's the effect of that? Would we consider it a fix that we'd want to backport? >> >> 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) > This is against Johannes' work, right? If this is a fix, likely it would be fixing 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware"), right? -- Cheers, David