From: Fabiano Rosas <farosas@suse.de>
To: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: qemu-devel@nongnu.org, armbru@redhat.com,
Juan Quintela <quintela@redhat.com>, Peter Xu <peterx@redhat.com>,
Leonardo Bras <leobras@redhat.com>,
Claudio Fontana <cfontana@suse.de>,
Eric Blake <eblake@redhat.com>
Subject: Re: [PATCH v2 06/29] migration: Add auto-pause capability
Date: Wed, 25 Oct 2023 10:57:12 -0300 [thread overview]
Message-ID: <87y1fqerev.fsf@suse.de> (raw)
In-Reply-To: <ZTjWV9wQ5obKTpOG@redhat.com>
Daniel P. Berrangé <berrange@redhat.com> writes:
> On Mon, Oct 23, 2023 at 05:35:45PM -0300, Fabiano Rosas wrote:
>> Add a capability that allows the management layer to delegate to QEMU
>> the decision of whether to pause a VM and perform a non-live
>> migration. Depending on the type of migration being performed, this
>> could bring performance benefits.
>
> I'm not really see what problem this is solving.
>
Well, this is the fruit of your discussion with Peter Xu in the previous
version of the patch.
To recap: he thinks QEMU is doing useless work with file migrations
because they are always asynchronous. He thinks we should always pause
before doing fixed-ram migration. You said that libvirt would rather use
fixed-ram for a more broad set of savevm-style commands, so you'd rather
not always pause. I'm trying to cater to both of your wishes. This new
capability is the middle ground I came up with.
So fixed-ram would always pause the VM, because that is the primary
use-case, but libvirt would be allowed to say: don't pause this time.
> Mgmt apps are perfectly capable of pausing the VM before issuing
> the migrate operation.
>
Right. But would QEMU be allowed to just assume that if a VM is paused
at the start of migration it can then go ahead and skip all dirty page
mechanisms?
Without pausing, we're basically doing *live* migration into a static
file that will be kept on disk for who knows how long before being
restored on the other side. We could release the src QEMU resources (a
bit) earlier if we paused the VM beforehand.
We're basically talking about whether we want the VM to be usable in the
(hopefully) very short time between issuing the migration command and
the migration being finished. We might be splitting hairs here, but we
need some sort of consensus.
next prev parent reply other threads:[~2023-10-25 13:58 UTC|newest]
Thread overview: 128+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-23 20:35 [PATCH v2 00/29] migration: File based migration with multifd and fixed-ram Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 01/29] tests/qtest: migration events Fabiano Rosas
2023-10-25 9:44 ` Thomas Huth
2023-10-25 10:14 ` Daniel P. Berrangé
2023-10-25 13:21 ` Fabiano Rosas
2023-10-25 13:33 ` Steven Sistare
2023-10-23 20:35 ` [PATCH v2 02/29] tests/qtest: Move QTestMigrationState to libqtest Fabiano Rosas
2023-10-25 10:17 ` Daniel P. Berrangé
2023-10-25 13:19 ` Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 03/29] tests/qtest: Allow waiting for migration events Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 04/29] migration: Return the saved state from global_state_store Fabiano Rosas
2023-10-25 10:19 ` Daniel P. Berrangé
2023-10-23 20:35 ` [PATCH v2 05/29] migration: Introduce global_state_store_once Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 06/29] migration: Add auto-pause capability Fabiano Rosas
2023-10-24 5:25 ` Markus Armbruster
2023-10-24 18:12 ` Fabiano Rosas
2023-10-25 5:33 ` Markus Armbruster
2023-10-25 8:48 ` Daniel P. Berrangé
2023-10-25 13:57 ` Fabiano Rosas [this message]
2023-10-25 14:20 ` Daniel P. Berrangé
2023-10-25 14:58 ` Peter Xu
2023-10-25 15:25 ` Daniel P. Berrangé
2023-10-25 15:36 ` Peter Xu
2023-10-25 15:40 ` Daniel P. Berrangé
2023-10-25 17:20 ` Peter Xu
2023-10-25 17:31 ` Daniel P. Berrangé
2023-10-25 19:28 ` Peter Xu
2023-10-23 20:35 ` [PATCH v2 07/29] migration: Run "file:" migration with a stopped VM Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 08/29] tests/qtest: File migration auto-pause tests Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 09/29] io: add and implement QIO_CHANNEL_FEATURE_SEEKABLE for channel file Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 10/29] io: Add generic pwritev/preadv interface Fabiano Rosas
2023-10-24 8:18 ` Daniel P. Berrangé
2023-10-24 19:06 ` Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 11/29] io: implement io_pwritev/preadv for QIOChannelFile Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 12/29] migration/qemu-file: add utility methods for working with seekable channels Fabiano Rosas
2023-10-25 10:22 ` Daniel P. Berrangé
2023-10-23 20:35 ` [PATCH v2 13/29] migration: fixed-ram: Add URI compatibility check Fabiano Rosas
2023-10-25 10:27 ` Daniel P. Berrangé
2023-10-31 16:06 ` Peter Xu
2023-10-23 20:35 ` [PATCH v2 14/29] migration/ram: Introduce 'fixed-ram' migration capability Fabiano Rosas
2023-10-24 5:33 ` Markus Armbruster
2023-10-24 18:35 ` Fabiano Rosas
2023-10-25 6:18 ` Markus Armbruster
2023-10-23 20:35 ` [PATCH v2 15/29] migration/ram: Add support for 'fixed-ram' outgoing migration Fabiano Rosas
2023-10-25 9:39 ` Daniel P. Berrangé
2023-10-25 14:03 ` Fabiano Rosas
2023-11-01 15:23 ` Peter Xu
2023-11-01 15:52 ` Daniel P. Berrangé
2023-11-01 16:24 ` Peter Xu
2023-11-01 16:37 ` Daniel P. Berrangé
2023-11-01 17:30 ` Peter Xu
2023-10-31 16:52 ` Peter Xu
2023-10-31 17:33 ` Fabiano Rosas
2023-10-31 17:59 ` Peter Xu
2023-10-23 20:35 ` [PATCH v2 16/29] migration/ram: Add support for 'fixed-ram' migration restore Fabiano Rosas
2023-10-25 9:43 ` Daniel P. Berrangé
2023-10-25 14:07 ` Fabiano Rosas
2023-10-31 19:03 ` Peter Xu
2023-11-01 9:26 ` Daniel P. Berrangé
2023-11-01 14:21 ` Peter Xu
2023-11-01 14:28 ` Daniel P. Berrangé
2023-11-01 15:00 ` Peter Xu
2023-11-06 13:18 ` Fabiano Rosas
2023-11-06 21:00 ` Peter Xu
2023-11-07 9:02 ` Daniel P. Berrangé
2023-10-31 19:09 ` Peter Xu
2023-10-31 20:00 ` Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 17/29] tests/qtest: migration-test: Add tests for fixed-ram file-based migration Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 18/29] migration/multifd: Allow multifd without packets Fabiano Rosas
2023-10-23 20:35 ` [PATCH v2 19/29] migration/multifd: Add outgoing QIOChannelFile support Fabiano Rosas
2023-10-25 9:52 ` Daniel P. Berrangé
2023-10-25 14:12 ` Fabiano Rosas
2023-10-25 14:23 ` Daniel P. Berrangé
2023-10-25 15:00 ` Fabiano Rosas
2023-10-25 15:26 ` Daniel P. Berrangé
2023-10-31 20:11 ` Peter Xu
2023-10-23 20:35 ` [PATCH v2 20/29] migration/multifd: Add incoming " Fabiano Rosas
2023-10-25 10:29 ` Daniel P. Berrangé
2023-10-25 14:18 ` Fabiano Rosas
2023-10-31 21:28 ` Peter Xu
2023-10-23 20:36 ` [PATCH v2 21/29] migration/multifd: Add pages to the receiving side Fabiano Rosas
2023-10-31 22:10 ` Peter Xu
2023-10-31 23:18 ` Fabiano Rosas
2023-11-01 15:55 ` Peter Xu
2023-11-01 17:20 ` Fabiano Rosas
2023-11-01 17:35 ` Peter Xu
2023-11-01 18:14 ` Fabiano Rosas
2023-10-23 20:36 ` [PATCH v2 22/29] io: Add a pwritev/preadv version that takes a discontiguous iovec Fabiano Rosas
2023-10-24 8:50 ` Daniel P. Berrangé
2023-10-23 20:36 ` [PATCH v2 23/29] migration/ram: Add a wrapper for fixed-ram shadow bitmap Fabiano Rosas
2023-11-01 14:29 ` Peter Xu
2023-10-23 20:36 ` [PATCH v2 24/29] migration/ram: Ignore multifd flush when doing fixed-ram migration Fabiano Rosas
2023-10-25 9:09 ` Daniel P. Berrangé
2023-10-23 20:36 ` [PATCH v2 25/29] migration/multifd: Support outgoing fixed-ram stream format Fabiano Rosas
2023-10-25 9:23 ` Daniel P. Berrangé
2023-10-25 14:21 ` Fabiano Rosas
2023-10-23 20:36 ` [PATCH v2 26/29] migration/multifd: Support incoming " Fabiano Rosas
2023-10-23 20:36 ` [PATCH v2 27/29] tests/qtest: Add a multifd + fixed-ram migration test Fabiano Rosas
2023-10-23 20:36 ` [PATCH v2 28/29] migration: Add direct-io parameter Fabiano Rosas
2023-10-24 5:41 ` Markus Armbruster
2023-10-24 19:32 ` Fabiano Rosas
2023-10-25 6:23 ` Markus Armbruster
2023-10-25 8:44 ` Daniel P. Berrangé
2023-10-25 14:32 ` Fabiano Rosas
2023-10-25 14:43 ` Daniel P. Berrangé
2023-10-25 17:30 ` Fabiano Rosas
2023-10-25 17:45 ` Daniel P. Berrangé
2023-10-25 18:10 ` Fabiano Rosas
2023-10-30 22:51 ` Fabiano Rosas
2023-10-31 9:03 ` Daniel P. Berrangé
2023-10-31 13:05 ` Fabiano Rosas
2023-10-31 13:45 ` Daniel P. Berrangé
2023-10-31 14:33 ` Fabiano Rosas
2023-10-31 15:22 ` Daniel P. Berrangé
2023-10-31 15:52 ` Fabiano Rosas
2023-10-31 15:58 ` Daniel P. Berrangé
2023-10-31 19:05 ` Fabiano Rosas
2023-11-01 9:30 ` Daniel P. Berrangé
2023-11-01 12:16 ` Fabiano Rosas
2023-11-01 12:23 ` Daniel P. Berrangé
2023-11-01 12:30 ` Fabiano Rosas
2023-10-24 8:33 ` Daniel P. Berrangé
2023-10-24 19:06 ` Fabiano Rosas
2023-10-25 9:07 ` Daniel P. Berrangé
2023-10-25 14:48 ` Fabiano Rosas
2023-10-25 15:22 ` Daniel P. Berrangé
2023-10-23 20:36 ` [PATCH v2 29/29] tests/qtest: Add a test for migration with direct-io and multifd Fabiano Rosas
2023-10-25 9:25 ` Daniel P. Berrangé
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