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 14002C27C4F for ; Wed, 26 Jun 2024 11:36:25 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sMQwE-0001rK-B8; Wed, 26 Jun 2024 07:35:46 -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 1sMQwB-0001qp-CO for qemu-devel@nongnu.org; Wed, 26 Jun 2024 07:35:43 -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 1sMQw2-0003w1-CQ for qemu-devel@nongnu.org; Wed, 26 Jun 2024 07:35:40 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1719401701; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kApg/k4JBXzGi94vq444VnfhbxVUpN4/B07npJ1wXZU=; b=NmKF2q4o13XAukZNE2zoBIdIT3zVh722OPURddQNFR99Uqm4u8OLka+8bVBH1VDT0XKAFp xRbmAadDVmrouMg39TukDppf4rtWFdoxh1LOzDIWKNckR+GBKhbY64kFUGfeeHem9/0sk2 U5rfQsaSESOYm3KKq0gawRKjM+uQfZ4= Received: from mx-prod-mc-03.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-626-lV1fTAVEPF-w3HphSRdI2Q-1; Wed, 26 Jun 2024 07:34:57 -0400 X-MC-Unique: lV1fTAVEPF-w3HphSRdI2Q-1 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AF93C19560B4; Wed, 26 Jun 2024 11:34:54 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.50]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C535C300021A; Wed, 26 Jun 2024 11:34:49 +0000 (UTC) Date: Wed, 26 Jun 2024 12:34:46 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Joao Martins Cc: Peter Xu , 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> <9b6c50d2-5c42-48b2-8e0b-b6304f225679@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <9b6c50d2-5c42-48b2-8e0b-b6304f225679@oracle.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 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: 10 X-Spam_score: 1.0 X-Spam_bar: + X-Spam_report: (1.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.207, 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=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 Wed, Jun 26, 2024 at 12:29:41PM +0100, Joao Martins wrote: > On 25/06/2024 19:37, Daniel P. Berrangé wrote: > > 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. > > > > The downtime limit is 300, it's more than you are giving something *extra* 10ms > when you switchover regardless of where that's spent. > > If it makes it easier to understand you could see this parameter as: > > 'downtime-limit-max-error' = 10 ms > > The name as proposed by the RFC was meant to honor what the error margin was > meant for: to account for extra time during switchover. Adding this inside > downtime-limit wouldn't work as it otherwise would be used solely for RAM > transfer during precopy. > > > 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. > > > That still happens with this patches, no specific budget is given to each. If no specific budget is given to each, then IMHO adding the second parameter is pointless & misleading. 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 :|