From: Peter Krempa <pkrempa@redhat.com>
To: Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
Cc: Juan Quintela <quintela@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
qemu-devel@nongnu.org, Peter Xu <peterx@redhat.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, Den Lunev <den@openvz.org>
Subject: Re: [PATCH v4 0/6] UFFD write-tracking migration/snapshots
Date: Thu, 26 Nov 2020 16:47:51 +0100 [thread overview]
Message-ID: <20201126154751.GH2366@angien.pipo.sk> (raw)
In-Reply-To: <20201126151734.743849-1-andrey.gruzdev@virtuozzo.com>
On Thu, Nov 26, 2020 at 18:17:28 +0300, Andrey Gruzdev via wrote:
> This patch series is a kind of 'rethinking' of Denis Plotnikov's ideas he's
> implemented in his series '[PATCH v0 0/4] migration: add background snapshot'.
>
> Currently the only way to make (external) live VM snapshot is using existing
> dirty page logging migration mechanism. The main problem is that it tends to
> produce a lot of page duplicates while running VM goes on updating already
> saved pages. That leads to the fact that vmstate image size is commonly several
> times bigger then non-zero part of virtual machine's RSS. Time required to
> converge RAM migration and the size of snapshot image severely depend on the
> guest memory write rate, sometimes resulting in unacceptably long snapshot
> creation time and huge image size.
>
> This series propose a way to solve the aforementioned problems. This is done
> by using different RAM migration mechanism based on UFFD write protection
> management introduced in v5.7 kernel. The migration strategy is to 'freeze'
> guest RAM content using write-protection and iteratively release protection
> for memory ranges that have already been saved to the migration stream.
> At the same time we read in pending UFFD write fault events and save those
> pages out-of-order with higher priority.
This sounds amazing! Based on your description I assume that the final
memory image contains state image from the beginning of the migration.
This would make it desirable for the 'migrate' qmp command to be used as
part of a 'transaction' qmp command so that we can do an instant disk
and memory snapshot without any extraneous pausing of the VM.
I'll have a look at using this mechanism in libvirt natively.
next prev parent reply other threads:[~2020-11-26 15:57 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-26 15:17 [PATCH v4 0/6] UFFD write-tracking migration/snapshots Andrey Gruzdev via
2020-11-26 15:17 ` [PATCH v4 1/6] introduce 'background-snapshot' migration capability Andrey Gruzdev via
2020-11-27 19:55 ` Peter Xu
2020-11-28 16:35 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 2/6] introduce UFFD-WP low-level interface helpers Andrey Gruzdev via
2020-11-27 21:04 ` Peter Xu
2020-11-29 20:12 ` Andrey Gruzdev
2020-11-30 15:34 ` Peter Xu
2020-11-30 18:41 ` Andrey Gruzdev
2020-12-01 12:24 ` Dr. David Alan Gilbert
2020-12-01 19:32 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 3/6] support UFFD write fault processing in ram_save_iterate() Andrey Gruzdev via
2020-11-27 21:49 ` Peter Xu
2020-11-29 21:14 ` Andrey Gruzdev
2020-11-30 16:32 ` Peter Xu
2020-11-30 19:27 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 4/6] implementation of background snapshot thread Andrey Gruzdev via
2020-11-26 15:17 ` [PATCH v4 5/6] the rest of write tracking migration code Andrey Gruzdev via
2020-11-27 22:26 ` Peter Xu
2020-11-30 8:09 ` Andrey Gruzdev
2020-11-26 15:17 ` [PATCH v4 6/6] introduce simple linear scan rate limiting mechanism Andrey Gruzdev via
2020-11-27 22:28 ` Peter Xu
2020-11-30 8:11 ` Andrey Gruzdev
2020-11-30 16:40 ` Peter Xu
2020-11-30 19:30 ` Andrey Gruzdev
2020-11-26 15:47 ` Peter Krempa [this message]
2020-11-27 8:21 ` [PATCH v4 0/6] UFFD write-tracking migration/snapshots Andrey Gruzdev
2020-11-27 9:49 ` Peter Krempa
2020-11-27 10:00 ` Andrey Gruzdev
2020-11-27 15:45 ` Peter Xu
2020-11-27 17:19 ` Andrey Gruzdev
2020-11-27 22:04 ` Peter Xu
2020-11-30 8:07 ` Andrey Gruzdev
2020-12-01 7:08 ` Peter Krempa
2020-12-01 8:42 ` Andrey Gruzdev
2020-12-01 10:53 ` Peter Krempa
2020-12-01 11:24 ` Andrey Gruzdev
2020-12-01 18:40 ` Dr. David Alan Gilbert
2020-12-01 19:22 ` Peter Xu
2020-12-01 20:01 ` Dr. David Alan Gilbert
2020-12-01 20:29 ` Andrey Gruzdev
2020-12-01 20:11 ` Andrey Gruzdev
2020-12-01 18:54 ` Peter Xu
2020-12-01 20:00 ` Dr. David Alan Gilbert
2020-12-01 20:26 ` Andrey Gruzdev
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201126154751.GH2366@angien.pipo.sk \
--to=pkrempa@redhat.com \
--cc=andrey.gruzdev@virtuozzo.com \
--cc=armbru@redhat.com \
--cc=den@openvz.org \
--cc=dgilbert@redhat.com \
--cc=pbonzini@redhat.com \
--cc=peterx@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=quintela@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).