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 289DF2C21F1; Fri, 17 Jul 2026 08:47:50 +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=1784278072; cv=none; b=etjSxueaMSmKEfulDFiJfrJQ+4/b5aVLHhV+qC9CoMsVusUeZZC1izRZTq5yI8w7doNbJr4ubjSTavjR7VVEAKZ/mVc01c02dzSjZ/QJpCiHOzuSSPoNXG/HkeHRK3Ob7ZTxtjj049QvJb3sMcjz2kFy7YrO7P7mgF4oO760ecw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784278072; c=relaxed/simple; bh=Np7IQ8IEu0RusFpuqJoQ1OWpIU9tI5HB4aOLC2XXgto=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Nguyt2yd50MCAI5JHT4Akxiw1IZHvvH/wOM+X/uvWSh/xU2FR0BpIZ7u6r7bHYTDmd4+yom5jccfLTVHRNAK1GPfi/l3TdcsUBILua8Whb36JDsJv6YVSASpOz/H5FTdNh2L6hdKwY460MAZ2XE4YdTX7NyiQaZehDTFlb62WBI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WmZ+jBwN; 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="WmZ+jBwN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 498FF1F000E9; Fri, 17 Jul 2026 08:47:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784278070; bh=Np7IQ8IEu0RusFpuqJoQ1OWpIU9tI5HB4aOLC2XXgto=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=WmZ+jBwNWeAxtyx5aezA6KyvkpfxVkaLqDEEG83OvsUOFT/+hXyWCxtGq6s2W0vs4 fQqwkRU8sPFkBslvvecyOFCbY81ghCcCvaBPgikt0CPJRyt9OiTCVULqPdRJQqMoSf I7a3iVmpD4XPKLggaaaTD3ilRukPIkMhoffU+/xffizr5uRp9k5gIwnh9N/f9vXV6G QEcy5C1AwagJAoqghnfI184o7x8HMHU6TyTAEbIdWFz4M/TtI/OlSYqeDun9seOh+4 hB4sQfXue19QvhUZHTcnI8az3dWPFp1SncgIg8zEylT4Isq24pHdB0yMrv7h0idsCu voQPyBqXUnuQQ== Date: Fri, 17 Jul 2026 09:47:31 +0100 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Ye Liu , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Andrew Morton , 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 Subject: Re: [PATCH] mm/thp: expose deferred split folio memory usage in meminfo Message-ID: References: <20260717063025.168436-1-ye.liu@linux.dev> <46017e29-48a3-4a74-8c5a-0be9d912deaa@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46017e29-48a3-4a74-8c5a-0be9d912deaa@kernel.org> On Fri, Jul 17, 2026 at 10:37:21AM +0200, David Hildenbrand (Arm) wrote: > 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, also this :) agree entirely. > > -- > Cheers, > > David Thanks, Lorenzo