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 2AE0EC4167D for ; Tue, 14 Nov 2023 10:45:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r2qv5-00026k-Si; Tue, 14 Nov 2023 05:45:23 -0500 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 1r2qv4-00026X-NT for qemu-devel@nongnu.org; Tue, 14 Nov 2023 05:45:22 -0500 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 1r2qv2-0003Cp-S4 for qemu-devel@nongnu.org; Tue, 14 Nov 2023 05:45:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1699958719; 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=IfIm0EU0aiwrv2O9PEMJ93kwNOEpPUNdT/Da/OsD1tI=; b=A55WUYp1ThDrghikIQCk+Qe0gm4AwUH1TbOfkWjADsOFPfMOAMFVF2Nr2YIxXx2AZizZO0 /Aeb7+Yw2EddawnrkF8mLIV77n3NomLwosk1R3J9syiM7PSeWGSAZ6GaLEfAuvs4g9s1Qw 8QJAzRHBrfCvMRN26ivVUnKjarivqbE= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-580-JGdKdvX2O_2UwkfxmqBu3Q-1; Tue, 14 Nov 2023 05:45:16 -0500 X-MC-Unique: JGdKdvX2O_2UwkfxmqBu3Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 10DAD29AA3B5; Tue, 14 Nov 2023 10:45:16 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.108]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D84F6C1596F; Tue, 14 Nov 2023 10:45:14 +0000 (UTC) Date: Tue, 14 Nov 2023 10:45:12 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Juan Quintela Cc: Markus Armbruster , Peter Xu , qemu-devel@nongnu.org, Fabiano Rosas , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Thomas Huth Subject: Re: Configuring migration Message-ID: References: <875y3dixzp.fsf@pond.sub.org> <8734yhgrzl.fsf@pond.sub.org> <877cnrjd71.fsf@pond.sub.org> <87zfzz82xq.fsf@secure.mitica> <87msvw6xm2.fsf_-_@pond.sub.org> <87pm0cochf.fsf@secure.mitica> <87h6loobu4.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87h6loobu4.fsf@secure.mitica> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 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: -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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Nov 14, 2023 at 11:42:27AM +0100, Juan Quintela wrote: > Daniel P. Berrangé wrote: > > On Tue, Nov 14, 2023 at 11:28:28AM +0100, Juan Quintela wrote: > >> Daniel P. Berrangé wrote: > >> > On Thu, Nov 02, 2023 at 03:25:25PM +0100, Markus Armbruster wrote: > >> >> Now let's try to apply this to migration. > >> >> > >> >> As long as we can have just one migration, we need just one QAPI object > >> >> to configure it. > >> >> > >> >> We could create the object with -object / object_add. For convenience, > >> >> we'd probably want to create one with default configuration > >> >> automatically on demand. > >> >> > >> >> We could use qom-set to change configuration. If we're not comfortable > >> >> with using qom-set for production, we could do something like > >> >> blockdev-reopen instead. > >> > > >> > Do we even need to do this via a QAPI object ? > >> > > >> > Why are we not just making the obvious design change of passing everything > >> > with the 'migrate' / 'migrate-incoming' commands that kick it off: > >> > > >> > ie: > >> > > >> > { 'command': 'migrate', > >> > 'data': {'uri': 'str', > >> > '*channels': [ 'MigrationChannel' ], > >> > '*capabilities': [ 'MigrateCapability' ], > >> > '*parameters': [ 'MigrateParameters' ], > >> > '*detach': 'bool', '*resume': 'bool' } } > >> > >> Once that we are doing incompatible changes: > > > > This is not incompatible - it is fully backcompatible with existing > > usage initially, which should make it pretty trivial to introduce > > to the code. Mgmt apps can carry on using migrate-set-capabilities > > and migrate-set-parameters, and ignore these new 'capabilities' > > and 'parameters' fields if desired. > > > > Only once we decide to deprecate migrate-set-capabilities, would > > it become incompatible. > > Oh, I mean that the interface is incompatible. Not that we can't do the > current one on top of this one. > > >> - resume can be another parameter > > > > Potentially yes, but 'resume' is conceptually different to all > > the other capabilities and parameters, so I could see it remaining > > as a distinct field as it is now > > It is conceptually different. But it is the _only_ one needed that > capability. And putting that on the parameters and just checking it > first will achieve the same result. I think that being special here > don't help, for instance, to check for incompatible things, we need to > also pass resume (it is only valid for postcopy). > > >> - detach is not needed. QMP don't use it, and HMP don't need to pass it > >> to qmp_migrate() to make the non-detached implemntation. > > > > We could deprecate that today then. > > Yeap. Will do it. > > >> > (deprecated bits trimmed for clarity) > >> > > >> > and the counterpart: > >> > > >> > { 'command': 'migrate-incoming', > >> > 'data': {'*uri': 'str', > >> > '*channels': [ 'MigrationChannel' ], > >> > '*capabilities': [ 'MigrateCapability' ], > >> > '*parameters': [ 'MigrateParameters' ] } } > >> > > >> > such that the design is just like 99% of other commands which take > >> > all their parameters directly. We already have 'migrate-set-parameters' > >> > remaining for the runtime tunables, and can deprecate the usage of this > >> > when migration is not already running, and similarly deprecate > >> > migrate-set-capabilities. > >> > >> This makes sense to me, but once that we change, we could try to merge > >> capabilities and parameters. See my other email on this topic. > >> Basically the distition is arbitrary, so just have one of them. > >> > >> Or better, as I said in the other email, we have two types of > >> parameters: > >> - the ones that need to be set before migration starts > >> - the ones that can be changed at any time > >> > >> So to be simpler, I think that 1st set should be passed to the commands > >> themselves and the others should only be set with > >> migrate_set_parameters. > > > > As a mgmt app dev I don't want there to be an arbitrary distinction > > between what I can pass with 'migrate' and what I have to use a > > separate command for. > > If it ever wants to set the parameter that it "can" change after > migration starts, it needs to know that they are different. > > Once told that, I don't write management apps and you do so I am not > discussing further O:-) > > > If I'm starting a migration, I just want to > > pass all the settings with the 'migrate' command. I should not have > > to care about separate 'migrate-set-parameters' command at all, unless > > I actually need to change something on the fly (many migrates will > > never need this). > > > What OpenStack/CNV do? > > If my memory is right, at least one of them used progressive downtimes > every couple of iterations or something like that. If they're using pre-copy, yes, they both can do progressive tuning. If using post-copy though, you potentially never need to change any tunable on the fly. 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 :|