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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 F35E0CDB471 for ; Tue, 23 Jun 2026 08:03:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=uGXAbbvDtMgdseoEBMP4tUzRSWv2MJSuTR3Me0ClWC8=; b=gHGkk3X6F1abztnHmqAOTWbrDR bhFU1biKF9La7xR17U7clOi/Y8iD8v7yusPh/tkixRWbZL0kwGv3tpkykFN67mH4U6c/YPkcxhnY8 Tz7Jr8+q6MjGmoXtjReefzOu/4L2AcYAH/vdvXYqJzmG6N0dBTxFgCuv4vsgpCZt9ALThnQ9s3Xz4 K3WXOw38jR6aYSN0CFoimJIsIa+TXl2UzXvSE93iqBPkKtbuptt/Sq5HKKHoUjGvRyPrqC8+lYr3+ 5A8Sj/avUxAoTm3GAJ3rI0wbH44AlMOmpWoZsaVo+L5IH1dLLClwcKowXsSRiZJMb2d+H792aHNfD JIAD1oFw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wbw5t-00000005s82-2x39; Tue, 23 Jun 2026 08:02:53 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wbw5s-00000005s7r-34Ae; Tue, 23 Jun 2026 08:02:52 +0000 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 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 X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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