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 5E756606A33A for ; Thu, 5 Nov 2026 14:03:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PBGMmnjh Received: by kanga.kvack.org (Postfix) id 3A2A36B05B8; Thu, 5 Nov 2026 09:02:56 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 354E36B05B9; Thu, 5 Nov 2026 09:02:56 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 28FDD6B05BA; Thu, 5 Nov 2026 09:02:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 052FC6B05B8 for ; Thu, 5 Nov 2026 09:02:55 -0500 (EST) Received: from smtpin25.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id E713BA0A4C for ; Thu, 5 Nov 2026 14:02:54 +0000 (UTC) X-FDA: 85401231468.25.18EEC42 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf17.hostedemail.com (Postfix) with ESMTP id 5AD4D40014 for ; Thu, 5 Nov 2026 14:02:53 +0000 (UTC) Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=PBGMmnjh; spf=pass (imf17.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793887373; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Zn4FGyqcpXuDOI4yAR+P0rUnqH2M0CuU1TGwYX3rR+o=; b=AXd3+iY743jYnX9eUlrhP3F0k9spI3tDiyssSVQJn7hMVZ+WXO2fSsKNu1G1tQ/QDfcCLP eYxdm7XoVRW26kFFhDfmdxM7ho2I1SRcnNrctfCrOV+d8ryCIslpCtbKELfY3/87G+RPfK G9Wz1D++eJAhF/drZr+m3OUvPDZl8Wc= ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=PBGMmnjh; spf=pass (imf17.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793887373; b=S3qGFXJhS2plN1HBTcCalkh2TiCkVgpWhIsPdGNiC1r0SLFek1jrbzKSh6cFUJ4Qt8wvfT 7U1t+qSYrulZWXdJaDatRtaTICZwTtnOTiAMOJ6ekIQ8rmtlLLl0F7oIavy67Co5A9CSVt XFs9C92bQLe8QDoHLbx85Fenp6yjOlc= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id D2F9160A97; Thu, 5 Nov 2026 14:02:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3A31E1F00919; Thu, 5 Nov 2026 14:02:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793887372; bh=Zn4FGyqcpXuDOI4yAR+P0rUnqH2M0CuU1TGwYX3rR+o=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=PBGMmnjhDZ38hOgzwbJkh3sIHEnlSGL9uYp2wngdD276txrDfZ30SbBzuawEV1nnq Rv0xUXVLJMiY178nhfx2khC2t9XI1dRXm6G5TlAoNS7YPerunjz7djsPlvLVZ0/C/k 26g4h1VjB/HlAFQV1zmssZ7NwOIYzsSSZb0yhkM1tOMG25faR5/ai3+x+Y/3RVOPDj gdYrprathq27egizqYSvwVuvU1wkKGxUxFpKE7ymPIMPn6A9ky5MdawMzjXl4/mefd pI0UAGhaO/oyhaxueCevuZ2zkOe8TTbhuwEgihtJKqK+ADu/Zx5bMOsVPAt+1bETdu NZoZqyIdegmtQ== Date: Thu, 5 Nov 2026 14:02:45 +0000 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kiryl Shutsemau , Andrew Morton , Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng , Waiman Long , Suren Baghdasaryan , Vlastimil Babka , Shakeel Butt , Yonghong Song , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH 4/5] mm: add and use mmap_read_lock[_killable]_nosteal() on contention Message-ID: References: <20261103-khugepaged-latency-fix-v1-0-a07ab16ac860@kernel.org> <20261103-khugepaged-latency-fix-v1-4-a07ab16ac860@kernel.org> <3a77219e-39e5-4e98-8f88-6f90bccf69f0@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3a77219e-39e5-4e98-8f88-6f90bccf69f0@kernel.org> X-Stat-Signature: dtb6d63ukr8agyq1ggrrmn35etmr9rbz X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 5AD4D40014 X-HE-Tag: 1793887373-798922 X-HE-Meta: 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 zWcpk3fA ZymCAV8fDbZ8DFXp+w/TPspfsk64ItVNOtakHBFYzsKJeEOOInKNjviEozqDg6XE9w4rUePB7fATYtpFDN6pb4XtMdM4Vr9Lv8K74Fh5dq5XN3IVP0IM0HYaSAR3Ez9302Vtd00mkDh6U+pZ6At4prUAg8954Q3cyi2lVIbQIT1vQ348op8vCbUaPruo35mxTUMTU50969CCtQ8OeZ8W/j2IXueKBjQ57VUm85/hnPs7XdTkVwQHds6X3PFdrRIsUVwE3PTBR4Z+eq9IUT1CicTNRJhPeJHafLCU2jlRob/NCd/Y1Dym/Vm7sIYSuWEI4d5wb 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 Thu, Nov 05, 2026 at 11:16:23AM +0100, David Hildenbrand (Arm) wrote: > On 11/3/26 09:27, Lorenzo Stoakes (ARM) wrote: > > With down_read[_killable]_nosteal() available, it becomes possible to > > release the mmap read lock in such a way that a queued write lock always > > takes precedence. > > > > Expose this to mm through two new wrappers - mmap_read_lock_nosteal() and > > mmap_read_lock_killable_nosteal(). > > > > Make use of this in scenarios where the mmap read lock is dropped > > explicitly for the purposes of relieving mmap_lock contention - the BPF > > task VMA iterator, and lock_next_vma_under_mmap_lock(), which is where > > /proc/$pid/smaps_rollup re-acquires the mmap lock after dropping it on > > contention and falling back from per-VMA locking. > > > > Signed-off-by: Lorenzo Stoakes (ARM) > > --- > > include/linux/mmap_lock.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ > > kernel/bpf/task_iter.c | 2 +- > > > I'd appreciate an ack from BPF folks and a confirmation that I could take this > through my tree :) With the rwsem thing as a separate patch this patch will be dropped in any case, which simplifies things :) -- Cheers, Lorenzo