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 CC3BCC88E45 for ; Fri, 11 Sep 2026 15:11:27 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B24076B0092; Fri, 11 Sep 2026 11:11:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AFA5C6B0095; Fri, 11 Sep 2026 11:11:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A106F6B0096; Fri, 11 Sep 2026 11:11:26 -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 8094D6B0092 for ; Fri, 11 Sep 2026 11:11:26 -0400 (EDT) Received: from smtpin13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 695C3140256 for ; Fri, 11 Sep 2026 15:11:25 +0000 (UTC) X-FDA: 85201820130.13.2BCF710 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf27.hostedemail.com (Postfix) with ESMTP id 969B44000A for ; Fri, 11 Sep 2026 15:11:23 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=mjk+54J5; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@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=1789139483; b=Nzin9QuVHFQrBXFT55oC9pCtQqUAhlKM6Y+0C/umNOjoMD86lsq/Pj/ypebJqqtvBFgAoU GEC+7RiFb6qrazniOkKUrPOU2ZIHMXy0quNkixOiRgW90k2f042RvsYA5BiwX/6seK+J86 7v+exoALb8+1A1ey088SuDzi1hcqiDQ= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=mjk+54J5; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@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=1789139483; 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=iu2JRtfBKdw5UgsTdTbkx1XDQxV98TajGeovQN2VTCg=; b=LtZN1TF+Y1B0wkMmQJHxC0zyw++bbMzS844Ogmi2MYWHIqpkZXTJTI/nOLsBXfBEhDBDm2 GDeSxPclLrjIeig1k/GmfWELiY3fHRDu5jHIv8MNk6Y4ozG/WvbTJf4c67FKoNVJ/Js/ZZ ZlRVXFVuF/5eyBoCmXKjs7rQuOncOBU= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6F0E54350E; Fri, 11 Sep 2026 15:11:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B6A81F000FF; Fri, 11 Sep 2026 15:11:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789139482; bh=iu2JRtfBKdw5UgsTdTbkx1XDQxV98TajGeovQN2VTCg=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=mjk+54J5E11AK3BFX4w4nNZOxHjiM64TNIKniajxes2e3pgfcqwMrSkU84pm3BHGh wZFXNRQva8aVjdC1fBCT0RwQIFXNhULvDiyNmfO+MIU0bcmyZWDoFqIJ8hFh/pE7Qo nTLsdGnbeqAROANpRP9aduKIbkejO1OOS3fi5Qvx43gaHaXRGMvMUCChyN6zcXLMap +aCvj9fE9dOHQUKP27oV4srfYDeUi92KNImyzbgpRqvM7f8XC1FM1YH4VG77RcuHYd hMITmvtrH5RxkU84V8Z1MJR1pZ7X5k/18GEZEnYxJkr8CzrfwpiYFxOAmmLJykMMUB hcFOnzqivZj9A== Message-ID: <9e902c8e-c825-45ee-89a1-85923453e43d@kernel.org> Date: Fri, 11 Sep 2026 17:11:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v4 0/12] mm: use per-VMA lock in __access_remote_vm for improved monitoring reliability To: Rik van Riel , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, Dave Hansen , Peter Zijlstra , Suren Baghdasaryan , Lorenzo Stoakes , Vlastimil Babka , "Liam R. Howlett" , Mike Rapoport , Michal Hocko , Jason Gunthorpe , John Hubbard , Peter Xu , Matthew Wilcox , Usama Arif References: <20260724222934.1463812-1-riel@surriel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260724222934.1463812-1-riel@surriel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 969B44000A X-Stat-Signature: dcbtgtwam13cf49n1cnxhhfe7sxitz6d X-Rspam-User: X-HE-Tag: 1789139483-653332 X-HE-Meta: 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 kvCSP6UJ 34NuwB1hLZv87f1qxlsugyQhiC2h5Da7JR4ofvHvPlbqaFtjDG1QTeRo91lFelTqULkbSNqX42/1atpq6VcGqvV4ivxGGcRq+kSDLu7j3YwF7Ix3GTAKsYsyLSos/N8/DfpTbdvUKQvuBTJB9PnO++ozCkr5mxcr8/erm5wewQNserpGXE+xwaPRVdwHBi+sZEQt2duUBmFOgj4kDFtwVOQXLSV9CvzPRYeOTpYXiW4bwFtoljTgkoLgReNcRt6VZSFx762L1mV61zi51UI2SjhDBpGgHfY+J4Zt/721+0AbHhrGD9CqpBIpfbZJVXSgyWcWX9DMYAxFnb+0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/25/26 00:29, Rik van Riel wrote: > __access_remote_vm() holds mmap_read_lock() for the whole transfer. On > large machines, with large multi-threaded applications, the mmap_lock > is often contended, leading to things like reads of /proc/PID/cmdline > stalling. > > This results in system monitoring tools getting stuck, right when > system information would be the most helpful. Rik, what's the status of this, and which series do you consider more relevant: the pure per-VMA lock change or the pure page-table walking + folio batching? I'd assume the page-table walking would result in more speedup and the per-VMA in mostly less contention. So likely we'd want the page-table walking optimization first. -- Cheers, David