From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id DF757606A31B for ; Tue, 20 Oct 2026 23:47:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=V20xcavw Received: by kanga.kvack.org (Postfix) id D8CFA6B0587; Tue, 20 Oct 2026 19:47:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D15FD6B0588; Tue, 20 Oct 2026 19:47:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BDF896B0589; Tue, 20 Oct 2026 19:47:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 9909D6B0587 for ; Tue, 20 Oct 2026 19:47:23 -0400 (EDT) Received: from smtpin02.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id ED7191401B7 for ; Tue, 20 Oct 2026 23:47:22 +0000 (UTC) X-FDA: 85344643524.02.C395D78 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf06.hostedemail.com (Postfix) with ESMTP id 2D615180003 for ; Tue, 20 Oct 2026 23:47:20 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=V20xcavw; dmarc=none; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1792540041; 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=8A2vMb2kidVxxepbgIC9HX3GXSZalF1YRLxBoNXtIqk=; b=yFkxASei0vT7QG6GQDX7Gt3VdHxtZdRGNeVO3jDVe4fLtRMQfwvnaoXF4FaGCYAR7Yg8C2 nFjcdrbZRPVY8HYYfOWeyBL9LLebzWR6JW2qVpx7EAx3QKORRAypIAcNNMa5uzf/XmsEYD jo2DP+innpmm6Lzlwvgp2S0N/xBMfJE= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=V20xcavw; dmarc=none; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1792540041; b=j1+0SMKnwirkCmQ8dECU5+H3CfxUG9f3qgRSSFr4FgjXzYcSvyUKu/BF9lWk4c2dvR/g6G MaC5WQCoDLwJVILNtfHFGjsUnnyyPl69kowxcB6O2gLTabhJoYU9Sx3j6ElLH36NJE0wDD CHkwJU668x1LA5eekmmltT5ieZzGHfQ= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 9032B42A50; Tue, 20 Oct 2026 23:47:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6CD91F000C9; Tue, 20 Oct 2026 23:47:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1792540039; bh=8A2vMb2kidVxxepbgIC9HX3GXSZalF1YRLxBoNXtIqk=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=V20xcavwH1fqcK9SSgsVtFQhUNOj+/hnoEuFSVhwaz8OlhyzfzmifNT4ZY38/nxEM akGiNYF2vhnAxVk5ZoMGFWPFLmHE71TO6qLMFb8uJhATBjoEOICMKK+8RF1R8fls66 gqmIUHwdtYb+EHT97CHm6YynQAUUyGOksSvAP0Z8= Date: Tue, 20 Oct 2026 16:47:18 -0700 From: Andrew Morton To: Barry Song Cc: Joanne Koong , linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Qi Zheng , Shakeel Butt , Roman Gushchin , Muchun Song , Zi Yan , Baolin Wang , Ryan Roberts , Usama Arif , Lance Yang , Hugh Dickins Subject: Re: [PATCH v3] mm: unqueue deferred split folios outside the lruvec lock Message-Id: <20261020164718.91017a58befc7940397ecd05@linux-foundation.org> In-Reply-To: References: <20261019230646.3510790-1-joannelkoong@gmail.com> <20261020153648.52636815691868735e9699be@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) X-Archived-By: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 2D615180003 X-Stat-Signature: zbprh1fwkdowp3rcmnq3btyh1irrga76 X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-8.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792540040-828912 X-HE-Meta: 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 hI28dDoO Kj4twczOgBqz3GAyLJu+nYSVCkXiX3TC3WSUr+c6ZDd/4YHtZPGLu7lX9lU7AUgwIn3mJdXHVFFmpe7sbwWoDR1xfYeEb/Ae/7VxAbFJPp2OPB6CQ9DMRL9f14IBaCdEPASDraDy8N0//xq2qEiqd5jLCXY1LA9xi7cpRWbTD0tOdYOaw7yrXjliMZFA2NuEk4BhzuuxZxJoRwEKnbxQNtcPHcdLEhXbD1Ed2SHkUtLdkb9FiopeAj304WxMl8thAu3PXocLGXah751h4rz3P8yj5GA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, 21 Oct 2026 06:40:23 +0800 Barry Song wrote: > > This is a speedup and not a correctness thing, yes? Let's make it a > > 7.4-rcX thing, for the 7.5 merge window. > > > > I'll park it in the mm-new branch for now. > > > > If people think the speedup is sufficiently worthwhile then I can add a > > cc:stable to it, if clear justification is included in the changelog. > > This isn't even a speedup at the moment, as no users have > adopted it yet. > > mTHP folios aren't currently added to the deferred split > queue. Joanne is about to add >=2MB mTHP folios to the > deferred split queue again, but even then, contention on > the queue shouldn't be an issue. > > It may become a problem someday when we add smaller large > folios, such as 16KB folios, to the deferred split queue. > So this patch is more about future-proofing. Oh. This: : This came out of the discussion on v2 of the mTHP shrinker series [1], : where queueing small mTHP folios on the deferred split queue was found : to regress Barry's fault microbenchmark. With [1] applied and : khugepaged/max_ptes_none=0 so that every folio is queued, perf lock : contention showed that the extra cost came from waiting on the lruvec : lock in the free path. made it sound like an unquantified speedup. Joanne, please clarify the expected impact (always) in the changelogging if there are reasons for a v4.