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 479D3C19F28 for ; Wed, 3 Aug 2022 17:37:05 +0000 (UTC) Received: from localhost ([::1]:57758 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oJIIq-00038Q-Bu for qemu-devel@archiver.kernel.org; Wed, 03 Aug 2022 13:37:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57844) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oJIGn-0000Uw-BN for qemu-devel@nongnu.org; Wed, 03 Aug 2022 13:34:59 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:46520) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oJIGk-0008Gw-8G for qemu-devel@nongnu.org; Wed, 03 Aug 2022 13:34:55 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659548093; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=5tYhhORvczuSFCpvq0wXlorMzP+MRrqaizFysH38+sU=; b=XaQvA868nMWuFirbTVMdTqvlqsx0aY0XOh/0Az8VLLZR+cfLd6Lm9GJpz0r6nFlwCEgzGV zgv8sVts29c8toRpdkAgkF/mI4gFrv8WS/KhECXtZ3cRNtWPdBejy4pJz64rhbeiYoWEIg aF2gH2S7Ny5rI15tAEh6dL+jnbrwrp8= 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-257-DBTNMbO2NsmcJuJhbjIpsA-1; Wed, 03 Aug 2022 13:34:50 -0400 X-MC-Unique: DBTNMbO2NsmcJuJhbjIpsA-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 D026C858EFF; Wed, 3 Aug 2022 17:34:49 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.173]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 38DEE2166B2A; Wed, 3 Aug 2022 17:34:48 +0000 (UTC) Date: Wed, 3 Aug 2022 18:34:45 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Claudio Imbrenda Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, david@redhat.com, cohuck@redhat.com, thuth@redhat.com, borntraeger@de.ibm.com, frankja@linux.ibm.com, alex.bennee@linaro.org Subject: Re: [PATCH v2 1/1] osdep: asynchronous teardown for shutdown on Linux Message-ID: References: <20220803173141.52711-1-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20220803173141.52711-1-imbrenda@linux.ibm.com> User-Agent: Mutt/2.2.6 (2022-06-05) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Aug 03, 2022 at 07:31:41PM +0200, Claudio Imbrenda wrote: > This patch adds support for asynchronously tearing down a VM on Linux. > > When qemu terminates, either naturally or because of a fatal signal, > the VM is torn down. If the VM is huge, it can take a considerable > amount of time for it to be cleaned up. In case of a protected VM, it > might take even longer than a non-protected VM (this is the case on > s390x, for example). > > Some users might want to shut down a VM and restart it immediately, > without having to wait. This is especially true if management > infrastructure like libvirt is used. > > This patch implements a simple trick on Linux to allow qemu to return > immediately, with the teardown of the VM being performed > asynchronously. > > If the new commandline option -async-teardown is used, a new process is > spawned from qemu at startup, using the clone syscall, in such way that > it will share its address space with qemu. > > The new process will then simpy wait until qemu terminates, and then it > will exit itself. > > This allows qemu to terminate quickly, without having to wait for the > whole address space to be torn down. The teardown process will exit > after qemu, so it will be the last user of the address space, and > therefore it will take care of the actual teardown. > > The teardown process will share the same cgroups as qemu, so both > memory usage and cpu time will be accounted properly. > > This feature can already be used with libvirt by adding the following > to the XML domain definition: > > > > How does this work in practice ? Libvirt should be blocking until all processes in the cgroup have exited, including this cloned child process. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|