From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-188.mta1.migadu.com (out-188.mta1.migadu.com [95.215.58.188]) (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 917B73C278B for ; Fri, 17 Jul 2026 09:31:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784280699; cv=none; b=TXnbTyFAVK3Q+3lPz9fFCoNM0KYRLDXdCWLbnEafhQNFp/pCkMAcz2YVFNOuxcTewLJtcXn/1U1NVy3fzkhDvCtt+nxXARCCfQgvkWOpmTgN7xa/SOebzELL4767m78tIzpIV6zjQifzE8BFJ9D4W3D4/cx4mjdplYjF41zfDTQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784280699; c=relaxed/simple; bh=Msi6FWOym7/XTmWIcpvni1Cd3C1PW2QCv4EMF0bzhZk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MP0VF72UjgD5Cgc6VLo8+ZkfBJM0FoKHsg0nUclywPvRzPFLb4THxVEG7er3u+VJWjYAKYzEN4/EDtILjdF2f5/PL3G9O+6tZQjULptxX516ULogUIxBbWZJHVC2MFA7cv6KhmB7F1KP50YHqRSANCNmEaS70K9fCYxw3rfqm5Y= 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=CKNwMd1O; arc=none smtp.client-ip=95.215.58.188 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="CKNwMd1O" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784280695; 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=OG6jvXmMMoQvaDYJwcula4TIxwe3WKsFp2ip9kul7ZE=; b=CKNwMd1OZtgv6WxEj0MvRApGEEyk7cRyetAls+cov9UTpb1CnVjUJCNEoCpm8SWQLMbmq+ Jq4RF1RTKmGUZWA6lBe03a6WyE2rZSTSgHrkzu63qBPxTAtctHBqESrmnZSKPalJfRK6J9 9fEgL+v817O3b3ruFs/yj+X2zSX8nXI= Date: Fri, 17 Jul 2026 17:31:11 +0800 Precedence: bulk X-Mailing-List: driver-core@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH] mm/thp: expose deferred split folio memory usage in meminfo To: "David Hildenbrand (Arm)" , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Andrew Morton , Lorenzo Stoakes Cc: Ye Liu , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Usama Arif , driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org References: <20260717063025.168436-1-ye.liu@linux.dev> <46017e29-48a3-4a74-8c5a-0be9d912deaa@kernel.org> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Ye Liu In-Reply-To: <46017e29-48a3-4a74-8c5a-0be9d912deaa@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 在 2026/7/17 16:37, David Hildenbrand (Arm) 写道: > On 7/17/26 08:30, Ye Liu wrote: >> From: Ye Liu >> >> Folios on the deferred split list hold physical memory that is >> invisible in meminfo. When a THP becomes partially mapped, the >> unmapped pages are removed from AnonPages but remain physically >> allocated until the shrinker splits the folio. This creates a >> memory accounting gap where used memory cannot be attributed to >> any meminfo field. >> >> Add NR_DEFERRED_SPLIT_PAGES to track the total memory consumed by >> folios currently on the deferred_split_lru, updated via >> mod_node_page_state() at all enqueue/dequeue points. The new field >> DeferredSplitPages is visible in /proc/meminfo, /proc/vmstat, and >> per-node /sys/devices/system/node/node*/meminfo. >> > > Oh no. > > This is really exposing a current implementation detail where we have this > information easily available in a way that we will not be able to change that > implementation later. > Yes, `/proc/meminfo` is a user-space ABI. Adding it there means you can't change the semantics, and the field will become unmaintainable, yet you can't delete it either. But I think this information is still necessary. Where would be a better place to put it? -- Thanks, Ye Liu