From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C1A02C44512 for ; Mon, 20 Jul 2026 02:36:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9E8446B0096; Sun, 19 Jul 2026 22:36:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9709A6B0098; Sun, 19 Jul 2026 22:36:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 83C5D6B0099; Sun, 19 Jul 2026 22:36:43 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 583EA6B0096 for ; Sun, 19 Jul 2026 22:36:43 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id C4F011C0A02 for ; Mon, 20 Jul 2026 02:36:42 +0000 (UTC) X-FDA: 85007591844.10.41917E1 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) by imf14.hostedemail.com (Postfix) with ESMTP id 12BCF100002 for ; Mon, 20 Jul 2026 02:36:40 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=eOkJFHgM; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf14.hostedemail.com: domain of ye.liu@linux.dev designates 95.215.58.187 as permitted sender) smtp.mailfrom=ye.liu@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784515001; h=from:from:sender: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:dkim-signature; bh=KusPc2Cpip6sPBv9PieUVxeP0LYiRvmdBMosAeD5k90=; b=zLn+kjloXqEuiEF64UiXRtgmBTlzWCMXToTGa637Lg5FeHBC7f8piQyQ+UDt00l+ZRLNKL E1bJlYcsStihVE/43O6vRAVIVjavuUFxErKxxteVXIB+u2jOTApDCCXVcjaq4ngpPwAtbB 7syTI3sdzwKp/Dp4/kfKuzJkw0iTkVo= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=eOkJFHgM; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf14.hostedemail.com: domain of ye.liu@linux.dev designates 95.215.58.187 as permitted sender) smtp.mailfrom=ye.liu@linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784515001; b=JTg86Svzv4U3Squ2U/TLR/1EFldakGMH2Q9qydQskyfiIbPg2853km9mwLd1K2kTulSXjy KNZsstNRQC4sWclXz5Wz0UWzMq5eDfZAwFF8vcY5llzSHmmRRea+vnrfqxs073MsS/0VAr 8DKQO410lRgQuEFLUeeWK02sQQ4U+2E= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784514998; 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=KusPc2Cpip6sPBv9PieUVxeP0LYiRvmdBMosAeD5k90=; b=eOkJFHgM6kcMlXyh79+foKL5z5ba2DkfV7iAXPTnhaKpSyAfu+A4jkqQyailvUNMc/6G4M zWGbF8zey1Q6P6wxgRW81ZPZq542iHED+d3N/jM8OdRtPmCigRL/bxu5+GnNbEoTTCgObo hFa9uZ3fDfD2zOrYYfaVO6DiCuPlLV4= Date: Mon, 20 Jul 2026 10:36:14 +0800 MIME-Version: 1.0 Subject: Re: [PATCH] mm/thp: expose deferred split folio memory usage in meminfo To: "David Hildenbrand (Arm)" , "Lorenzo Stoakes (ARM)" Cc: 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 References: <20260717063025.168436-1-ye.liu@linux.dev> <46017e29-48a3-4a74-8c5a-0be9d912deaa@kernel.org> <41bc5ca5-08ed-4aba-86a3-d7f44b16e6f5@linux.dev> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: sb8fzpsfupj8tb317tc91wpumfnr4kdd X-Rspamd-Queue-Id: 12BCF100002 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1784515000-527991 X-HE-Meta: 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 1KE2/+Mz jBSWCQwMUazkOSzqEnCMMHrbsUQoEuJrZURohZVWo5QL5c+dwvBQMgMorwxzCSTwiko4f8zPdx6LSfLgSwm11Ajkq381NW6gNJh663ft4WT4SufEIhH6Bl5oy0jKTt5SPsm55FV3089JvgrKDvVlWCgq3RbviPX2QhAysn7BXQAkmzPjps1g+44i3Sgx3nN4c4WJXuWyN2ew8mlI7TWVEB0u8SeVENjgZO1aYhjMnxPgw0sU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/7/17 18:29, David Hildenbrand (Arm) 写道: > On 7/17/26 11:54, Ye Liu wrote: >> >> >> 在 2026/7/17 17:48, Lorenzo Stoakes (ARM) 写道: >>> On Fri, Jul 17, 2026 at 11:33:05AM +0200, David Hildenbrand (Arm) wrote: >>>> >>>> Don't expose it to user space. >>> >>> Yeah please stop. >>> >>> We don't want this change, it exposes internal implementation details. It's a >>> no. >>> >>> Next time send an RFC or a discussion thread. >>> >> Yes, sending an RFC would be more appropriate. >> >> I'd also like to ask if it's possible to implement this in >> `/sys/kernel/debug/deferred_split_pages`, or are you completely against querying this statistic? > > It's not pages. It's folios. > > You don't know how much memory is there to reclaim. You don't know if it can > even be reclaimed. > > You don't even know if there can be any memory reclaimed *at all*, because there > are scenarios where we add folios that are actually *not* partially mapped today. > > You don't even know the relationship to memcgs. > >> >> How can we quickly identify this situation? >> I believe some people will still be confused: where did the memory go? > > Just like other caches that are shrunk on memory pressure. > > We do have a "split_deferred" and a "nr_anon_partially_mapped" counter in > "/sys/kernel/mm/transparent_hugepage/hugepages-2048kB/", maybe that helps. > Thank you, it really helped. -- Thanks, Ye Liu