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 6A74E407CE2; Wed, 3 Jun 2026 08:03:08 +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=1780473789; cv=none; b=HeFP9Bb2pO61/uUY2KUao7ZWadofoTXsL1yi+4wiP/9ufBgxvxi53go0BPKB5VENQrjRrEO2RbqhkJLBuni58TYOlM4yGK9WRUrbPcrBIIUfESmYXL+W3aihSFgTcCJ8ntfYgAKci/THGxZ1UrZrce0RpB6KQZYYc9EwUqN7OTA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780473789; c=relaxed/simple; bh=qWPpCg+e8pAoFNl3Pxs8PtfzF1KTT18RGKSwmrXhurc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sRbZ1bPIpVqLGnMbd7jXilepG3IgcqQWQw9UrYay+mublDljnX1rikHm6MXQa7V4Tgt289qadqSCUQtKyye51Qo9oihu+ME/t3R4eDVJZRjYHWp5FXP5g6M/98Wbqjdy5mSUxAiLtnSpXm5U2Cx9TQBioE8X03yE5yZEXka+ESY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VKj6Rfrg; 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="VKj6Rfrg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A9441F00898; Wed, 3 Jun 2026 08:03:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780473788; bh=LTJYCksleeQZKtt5TSmRNFAkMP5Na0YE2idGvPI9oDk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=VKj6Rfrgsp6QP0eG7Y3A+lrDbhLZF4gwVt/aPAAjjvBEnqcEM/PpY+m+gEIyDlqMc jzbk4H6ZNQAcIQ9wSYXBuputJZPcep4pMsKflExIXshMbs5gHH1CVyE/ZJpowNn7U3 JW3rHZPfNAa+Tqz/3Ac8PcTcMhIp+oaY9NhAK3nANzSpUb9j3jI6ieisZ5hUy+CD33 5713rY047/9h+3YZqKvJgH5yDr96rT8xGCu71YVr1v3jisS1W+iYaRVYz5EPWRjv84 8jKogWkE8hAHlvTmgW4S65PWk55R43ihnb8vOQIxo6/FEM6p1OqLvjdh9pDGLxuVrx BgINdphckN48A== Message-ID: Date: Wed, 3 Jun 2026 10:02:59 +0200 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 1/1] mm/thp: clear deferred split shrinker bits when queues drain To: Lance Yang , Andrew Morton 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, Johannes Weiner References: <20260602043453.67597-1-lance.yang@linux.dev> <20260602133706.d737a82858d1cf89870521b1@linux-foundation.org> 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 6/3/26 04:00, Lance Yang wrote: > > > 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 :) Right, I conclude that this can be a separate patch on top. -- Cheers, David