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 629E2C30653 for ; Tue, 25 Jun 2024 21:08:10 +0000 (UTC) Received: from [::1] (helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sMDBM-0001N8-3D; Tue, 25 Jun 2024 16:54:34 -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 1sMDB1-0001Ld-Aq for qemu-devel@nongnu.org; Tue, 25 Jun 2024 16:54:07 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sMDAJ-0003Ww-Pu for qemu-devel@nongnu.org; Tue, 25 Jun 2024 16:53:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719348732; 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=FnEow6ItVCsHy3Wj8fYlpWX03DfWKKdSG2Ud1N0AXcs=; b=Z/OE3OvAa0nQJg6wZU8zERsbzQbn3YTnM9sJcKBd8eVBL8LKae0j6gxqTwRdgLdabtjoxa bOD32Ub9olt06ejYzwhT4IWiLXORHrbfkDKANbYvHPH7Jmd6xWlQ89qTbnmqAtqhiiFz8O 8yFuMyZId4olXJfWItdO6CRqhWEUDc8= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-92-jYAau6XdMRmHZp7zFd2L-w-1; Tue, 25 Jun 2024 14:37:51 -0400 X-MC-Unique: jYAau6XdMRmHZp7zFd2L-w-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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 mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DA52B1955BDB; Tue, 25 Jun 2024 18:37:49 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.31]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ED0431956050; Tue, 25 Jun 2024 18:37:45 +0000 (UTC) Date: Tue, 25 Jun 2024 19:37:42 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Joao Martins , Elena Ufimtseva , qemu-devel@nongnu.org, eduardo@habkost.net, marcel.apfelbaum@gmail.com, philmd@linaro.org, wangyanan55@huawei.com, farosas@suse.de, eblake@redhat.com, armbru@redhat.com Subject: Re: [PATCH RFC 2/2] migration: abort on destination if switchover limit exceeded Message-ID: References: <20240621143221.198784-1-elena.ufimtseva@oracle.com> <20240621143221.198784-3-elena.ufimtseva@oracle.com> <9eeea2a9-b3ef-4791-94de-fb06ad2bd9b4@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 13 X-Spam_score: 1.3 X-Spam_bar: + X-Spam_report: (1.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_SBL_CSS=3.335, T_SPF_HELO_TEMPERROR=0.01, T_SPF_TEMPERROR=0.01 autolearn=no 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Jun 25, 2024 at 10:53:41AM -0400, Peter Xu wrote: > Then the question is how should we suggest the user to specify these two > parameters. > > The cover letter used: > > migrate_set_parameter downtime-limit 300 > migrate_set_parameter switchover-limit 10 What this means is that in practice the total downtime limit is 310 ms, however, expressing this as two parameters is incredibly inflexible. If the actual RAM transfer downtime only took 50 ms, then why should the switchover downtime still be limited to 10ms, when we've still got a budget of 250 ms that was unused. IOW, if my VM tolerates a downtime of 310ms, then I want that 310ms spread across the RAM transfer downtime and switchover downtime in *any* ratio. ALl that matters is the overall completion time. IMHO exposing 2 distinct parameters is horrible from a usability POV. 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 :|