From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5926E3C4B93; Tue, 23 Jun 2026 08:02:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782201773; cv=none; b=N6IjYTLcLZSa3aQEa8hGf+SYbxeM7EwoaCuRc+GVXboNFivUsb4pWPdoDVRnyf4Gf1zLISsANsP/a++g/dSwKT68OMcHLR7vrIOn0LZhzDhPdeFB6yDliKYk38caTPISFAqdBduLNXV0CJ8X719SQ0SyTlboUyi3cNCnRLSh5R8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782201773; c=relaxed/simple; bh=qKSmb2rf/MYen8UjnYMNdVit/7nvn1RbEp4Fg6ok5LQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=b5HKyg4u5F0d9qlFqjla/k8yYuY34zkvO6SX+iYjP5vJ/YmeinVH5Qx3bmIjI/j2ZVKNRBKLtarxs4kpRzeJgcc8yKom5IjFsmFsP8hUKGMvR4M3kdeWSxkDJSE2mWxl3VSYjnGBRLOtKiXkjXZAef3PFHnMnQ90QVuTCuio2gA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FklgZfZv; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FklgZfZv" 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 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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; 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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