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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6BEFACD4F26 for ; Tue, 23 Jun 2026 08:02:58 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4gkyH44hbxz2y71; Tue, 23 Jun 2026 18:02:56 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip="2600:3c0a:e001:78e:0:1991:8:25" ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1782201776; cv=none; b=QrJ01Anlnit5NhmKhfrtGdvjdyzprmSR1kQ9XNB/OFaOqPA/NcqFJX5heBdn0Fey+P9+8QecLKfJVudGy8QT84exm3eN9EH5Ywr7Jkja0WpSBGQfZjpfc9wCIXviT8jJBUnGz5Poq2gIi8CrcEU0HrcF+JxDVyTvTTfZpcgIYj2jRhZ6jMI5HLzXBHGY9fuhLcMbgeZS7TkIVe4V3o0fxLmKEhs/k099Q/1M+6Jdptr5j89khud2KfNQkHcNqXyOhuQFLr71uXvmKLjrSimRgBatx+4y8HA05MYFpHfaeaVM2ljSVAaU2R4c8cx1TdRjnhHsJMttOoNRXvs7r9gIYg== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1782201776; c=relaxed/relaxed; bh=uGXAbbvDtMgdseoEBMP4tUzRSWv2MJSuTR3Me0ClWC8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SLYV/jCW5E5d4QA0Vm9DkbgyEGjsPPNIqBYIPHonrzJrTTejm84wlZC87Tr8bd+xnk6mdJoNfEYuJVr72CZw7hQLwIadPkKr2rdhrmDd5DweGCl8Kuk+Wz0A3Cdu7rB4EG46UHWJVQysCojrcX84lMKeJwqoHgGLw6+CL0cQeL4tCALoGYj9vkK3KrNRiu2z9peJxGVc8qCqL04VKfReTBWMba/oc791M5sxly4g+L8ovJdzYMfsHk3d7lTzBaa19iYg1JeyUSdMR7Yf/iD+hjY/+L9IoR9wa+ScPWhCOZmnccui4iWNViJUbrFQeSnpYA6ESwqz/HpDzNomByYHtA== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=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=FklgZfZv; dkim-atps=neutral; spf=pass (client-ip=2600:3c0a:e001:78e:0:1991:8:25; helo=sea.source.kernel.org; envelope-from=david@kernel.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=FklgZfZv; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=2600:3c0a:e001:78e:0:1991:8:25; helo=sea.source.kernel.org; envelope-from=david@kernel.org; receiver=lists.ozlabs.org) Received: from sea.source.kernel.org (sea.source.kernel.org [IPv6:2600:3c0a:e001:78e:0:1991:8:25]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4gkyH31X2Qz2xwL for ; Tue, 23 Jun 2026 18:02:55 +1000 (AEST) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0C6A2437DF; Tue, 23 Jun 2026 08:02:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 986D81F000E9; Tue, 23 Jun 2026 08:02:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782201771; bh=uGXAbbvDtMgdseoEBMP4tUzRSWv2MJSuTR3Me0ClWC8=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=FklgZfZvf9emq2gmny2eGq6EMuPFgTPg3jmwAxmLaYfdeYYOx9o/LUsxGSyhC90Aj wyT19RvXdWlMCbyU9x5qRfWKwzHtDUwLyiTaRdHPzlhCnqASxByUiH+reBxZa6dm6/ 2eUrKJ7Sl3Ard2QCWFs5RMYz0cEIAQCf+F3cTsedtE8mzwpzHancQo4aEImHF0L8cr Fy0cEII7dznV9is/6QM/nYIXsQ76KUnc8J3lz0n9fEPXD9BgbtOHKKHco2unHFN5KT hMyDhDgPqCuk0aLgK7toBqI2XUvKRYcOcAAOK274SYOnvXU30gUDeEG5XgOjyI10Dd 19K+31feZDQsg== Message-ID: Date: Tue, 23 Jun 2026 10:02:40 +0200 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/5] mm: reduce mmap_lock contention and improve page fault performance To: Hongru Zhang Cc: akpm@linux-foundation.org, baohua@kernel.org, bhe@redhat.com, chentao@kylinos.cn, chrisl@kernel.org, jack@suse.cz, kasong@tencent.com, kunwu.chan@gmail.com, liam@infradead.org, lianux.mm@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, liyangouwen1@oppo.com, ljs@kernel.org, loongarch@lists.linux.dev, mhocko@suse.com, nphamcs@gmail.com, nzzhao@126.com, pfalcato@suse.de, rppt@kernel.org, shikemeng@huaweicloud.com, surenb@google.com, vbabka@kernel.org, wanglian@kylinos.cn, willy@infradead.org, youngjun.park@lge.com References: <3be9475b-0e8a-4df8-a130-4262f993973d@kernel.org> <20260623075805.466317-1-zhanghongru@xiaomi.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: <20260623075805.466317-1-zhanghongru@xiaomi.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 6/23/26 09:58, Hongru Zhang wrote: >> On 5/20/26 23:15, Matthew Wilcox wrote: >>> >>> all of the applications i run are either single threaded or don't fork. >>> what multithreaded applications call fork? >> >> Traditionally the problem was random libraries using fork+execve to launch other >> programs ... instead of using alternatives like posix_spwan (some use cases >> require more work done before execve and cannot yet switch to that). I'd hope >> that that is less of a problem on Android. >> >> I assume Android zygote might be multi threaded? Maybe sshd as well? Systemd? >> But I'd be surprised if there are really performance implications. >> >> Not sure about webbroswers .... I think most of them switched to fork servers, >> where I would assume fork servers would be single-threaded. >> >> So, yeah, getting a clear understanding how this ends up being a problem on >> Android would be great. > > Barry asked me to share observations on fork() usage across Android > applications. > > I wrote a BPF-based tracing tool (kprobe on copy_process, checking > CLONE_VM to distinguish process creation from thread creation) and ran > it against the top 200 Android applications in the China market during > normal usage scenarios. > > Results: > - 82 out of 200 apps (41%) call fork() during normal operation Crazy. Thanks for these numbers. > - Among these, some call fork() from multiple threads > > These are not zygote forks — they are fork() calls initiated by app > threads at runtime. Examples by category: > > Browsers: com.quark.browser, com.UCMobile, com.xunlei.browser > Shopping: com.taobao.taobao, com.tmall.wireless, com.achievo.vipshop > Video: com.youku.phone, com.qiyi.video, com.hunantv.imgo.activity > Social/IM: com.alibaba.android.rimet, com.ss.android.lark > News: com.ss.android.article.news, com.ss.android.article.lite > Navigation: com.autonavi.minimap, com.sdu.didi.psnger > Finance: com.eg.android.AlipayGphone, com.chinamworld.main I know that especially browser usually use fork servers: a tiny (single-threaded) process just to create new child processes. Any information regarding the apps above that use fork() on small vs. large processes? > > This confirms that fork() is widely used in real-world multi-threaded > Android applications. Above you write "some call fork() from multiple threads". Any further information on that? -- Cheers, David