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.gnu.org (lists.gnu.org [209.51.188.17]) (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 DDEB6EB64D9 for ; Mon, 10 Jul 2023 06:08:32 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qIk3n-0002Bb-B9; Mon, 10 Jul 2023 02:07:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qIk3m-0002BS-23 for qemu-devel@nongnu.org; Mon, 10 Jul 2023 02:07:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qIk3h-0001bv-36 for qemu-devel@nongnu.org; Mon, 10 Jul 2023 02:07:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688969254; h=from:from: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; bh=JyghLe8ySD12gm6LLOQqPPVb1CaqSNfRd4Yr5D8+m5o=; b=TbuI/HT8zVlAEgkiHyDFEqNJhiYTcx1Pmrip7HZIwEQ17M6/A79S9bOrYzc+IA3cftCmNG g1PUbiYX5NoHuF9DlT3e5DXsFuwjkGS4qjLVzItPs/MIk+uj40rAU6sSYcaP22o3fCeqR2 UeCoygZTAjSZZI+xgA8VZv2oMtpBfAA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-9-idIsnCRNOP-NXj0w2mrn2g-1; Mon, 10 Jul 2023 02:07:33 -0400 X-MC-Unique: idIsnCRNOP-NXj0w2mrn2g-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9AE91858290; Mon, 10 Jul 2023 06:07:32 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.65]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E5A2E2166B27; Mon, 10 Jul 2023 06:07:31 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E131F21E6A1F; Mon, 10 Jul 2023 08:07:30 +0200 (CEST) From: Markus Armbruster To: Jason Wang Cc: Bin Meng , Bin Meng , qemu-devel@nongnu.org, Richard Henderson , Zhangjin Wu , Claudio Imbrenda , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , "Edgar E. Iglesias" , Kevin Wolf , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , "Michael S. Tsirkin" , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Thomas Huth , Xuzhou Cheng Subject: Re: [PATCH v4 0/6] net/tap: Fix QEMU frozen issue when the maximum number of file descriptors is very large References: <20230628152726.110295-1-bmeng@tinylab.org> Date: Mon, 10 Jul 2023 08:07:30 +0200 In-Reply-To: (Jason Wang's message of "Mon, 10 Jul 2023 11:05:38 +0800") Message-ID: <87mt04b8pp.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Jason Wang writes: > On Sun, Jul 9, 2023 at 11:48=E2=80=AFPM Bin Meng wro= te: >> >> On Wed, Jun 28, 2023 at 11:29=E2=80=AFPM Bin Meng wr= ote: >> > >> > >> > Current codes using a brute-force traversal of all file descriptors >> > do not scale on a system where the maximum number of file descriptors >> > is set to a very large value (e.g.: in a Docker container of Manjaro >> > distribution it is set to 1073741816). QEMU just looks frozen during >> > start-up. >> > >> > The close-on-exec flag (O_CLOEXEC) was introduced since Linux kernel >> > 2.6.23, FreeBSD 8.3, OpenBSD 5.0, Solaris 11. While it's true QEMU >> > doesn't need to manually close the fds for child process as the proper >> > O_CLOEXEC flag should have been set properly on files with its own >> > codes, QEMU uses a huge number of 3rd party libraries and we don't >> > trust them to reliably be using O_CLOEXEC on everything they open. >> > >> > Modern Linux and BSDs have the close_range() call we can use to do the >> > job, and on Linux we have one more way to walk through /proc/self/fd >> > to complete the task efficiently, which is what qemu_close_range() >> > does, a new API we add in util/osdep.c. >> > >> > V1 link: https://lore.kernel.org/qemu-devel/20230406112041.798585-1-bm= eng@tinylab.org/ >> > >> > Changes in v4: >> > - add 'first > last' check logic >> > - reorder the ifdefs logic >> > - change i to unsigned int type >> > - use qemu_strtoi() instead of atoi() >> > - limit last upper value to sysconf(_SC_OPEN_MAX) - 1 >> > - call sysconf directly instead of using a variable >> > - put fd on its own line >> > >> > Changes in v3: >> > - fix win32 build failure >> > - limit the last_fd of qemu_close_range() to sysconf(_SC_OPEN_MAX) >> > >> > Changes in v2: >> > - new patch: "tests/tcg/cris: Fix the coding style" >> > - new patch: "tests/tcg/cris: Correct the off-by-one error" >> > - new patch: "util/async-teardown: Fall back to close fds one by one" >> > - new patch: "util/osdep: Introduce qemu_close_range()" >> > - new patch: "util/async-teardown: Use qemu_close_range() to close fds" >> > - Change to use qemu_close_range() to close fds for child process effi= ciently >> > - v1 link: https://lore.kernel.org/qemu-devel/20230406112041.798585-1-= bmeng@tinylab.org/ >> > >> > Bin Meng (4): >> > tests/tcg/cris: Fix the coding style >> > tests/tcg/cris: Correct the off-by-one error >> > util/async-teardown: Fall back to close fds one by one >> > util/osdep: Introduce qemu_close_range() >> > >> > Zhangjin Wu (2): >> > util/async-teardown: Use qemu_close_range() to close fds >> > net: tap: Use qemu_close_range() to close fds >> > >> >> Ping for 8.1? > > Queued. There are review questions open on PATCH 4+5.