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 32B4CCDB47F for ; Thu, 25 Jun 2026 06:32:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E24136B00A9; Thu, 25 Jun 2026 02:32:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DD4E86B00AB; Thu, 25 Jun 2026 02:32:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CC49A6B00AC; Thu, 25 Jun 2026 02:32:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id A573D6B00A9 for ; Thu, 25 Jun 2026 02:32:52 -0400 (EDT) Received: from smtpin22.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 13B75405EE for ; Thu, 25 Jun 2026 06:32:52 +0000 (UTC) X-FDA: 84917466984.22.49487DE Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf08.hostedemail.com (Postfix) with ESMTP id 5B473160008 for ; Thu, 25 Jun 2026 06:32:50 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=d8U5nipV; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1782369170; b=RjwVzRuWNXz2Zt/9S2PQzVfeNdkqtvUvlTgTlHxqS3xLdgxnlQVT6opUnNpHhZ7wmZEEoX rQHA/+BD+QLC4QglgCA6ipaStWynKegr1NUlFmmqQi0BMOZK2pranbt7GLbGuQexAni5Eb 45zG2hZkgmuw2fVi820cYJLvxIIq+9g= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1782369170; 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=f/AEKku/ZQdImcC1jUEB+o6t1SbIl/kNAaxzOYgG05I=; b=ulbPdG/aKjv0pKZcbjO/rATIL3TVPv4l4QctfnZFceVQq5XvfP/r1tMzOiDvwdp26bb5Ms uA+kb6rNDu3vLKGEoT1yndkGn0FMyVhvcswVaCX5qqhnqvnwNFaTsgxBmt172myrJtr4C1 9B6jH2wX0Zn/9hfVGA6IVVFHEaqfXR8= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=d8U5nipV; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id DDAE4600FC; Thu, 25 Jun 2026 06:32:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 424561F00A3A; Thu, 25 Jun 2026 06:32:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782369169; bh=f/AEKku/ZQdImcC1jUEB+o6t1SbIl/kNAaxzOYgG05I=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=d8U5nipVGbibZ8EDMf74Wqs9Mfxu2oApLifwMREzTIXxKzZkE40S03k8O3QtQcyzg syBDSAbvB+kmTUo7PGcVl2KN6qD1nG4d50+97PjgzxTtiO5K4PW8D19BpYIPDq+coZ vsvnWlczWbY0iI+HUWqab3/J/0NVbVe9xmQPfii8XqTsOaIVGYobjP2YFjcRC/bmCJ dDH701Jqni3K3yjyObKXbB1N4kG9DeAglTm3YWRArYj7OcWcJYNfMa/MCursLKrEvx yLqCVOnVzfE2YrLmFiXZNIw0086btyWO5setQa2ovvpNQI1/qkYJtgEYDGYbi6n8n/ zdA9VnyeJ42sQ== Message-ID: Date: Thu, 25 Jun 2026 08:32:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] mm: __access_remote_vm with per-VMA lock To: Rik van Riel , linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Dmitry Ilvokhin , Borislav Petkov , Dave Hansen , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , kernel-team@meta.com References: <20260625015053.2445008-1-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: <20260625015053.2445008-1-riel@surriel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 5B473160008 X-Stat-Signature: oz1n33pcxbygqyz7tkyxfohqa6kerkpt X-HE-Tag: 1782369170-636955 X-HE-Meta: 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 Pz4YWUB7 TqWmXY3mxKepJMg4uGyjImm/RkHrBUJ+UbLrphaCpv+IaWuo4ykbF/zTBGEjVtEtl2T0EGXMfNQ/Y1UEQrYC6rgIUQP75/qrXDxkXrXMb4BlklTWu1zYQaY4iIc8fhOrENwWaOVijefapu5K5sJzbXBk9X8JUkI4/1CcQKMwZpCqqHsGFFcTcyoj3jWF7/nQmwjvy+5jCOgW0gJHG3aCHu1CkKRfM8oX+ZHbGT76AA1eoMP5SBQYrSxZKjDfXsgk/65kPTtdVSW+/dN9ZBbr1VOWmAdPn2A0DV50YFBeZjVFFcLp9azUJZ0YQ2g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/25/26 03:50, Rik van Riel wrote: > Sometimes processes can get stuck with the mmap_lock held for > a long time. This slows down, and can even prevent system monitoring > tools from assessing and logging the situation, because they themselves > end up getting stuck on the mmap_lock. > > However, with the introduction of per-VMA locks, we can improve the > reliability of system monitoring, and generally speed up __access_remote_vm > under mmap_loc contention, by adding a fast path that does not require > the process-wide mmap_lock. > > This fast path is only compiled in and used when it is safe to do so, > meaning a kernel with per-VMA locks, RCU pgae table freeing, the VMA > is not hugetlbfs, iomap, pfnmap, etc... > > v2: > - simplify the code, which should be ok because these copies are < PAGE_SIZE > - clean up the code > - fix locking wrt tlb_remove_table_sync_one() > - hopefully address all the other comments You mean, ignoring my comments about not reiplementing GUP entirely? NAK -- Cheers, David