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Re: [RFC 1/6] migration: skipped field is really obsolete.
From: |
Juan Quintela |
Subject: |
Re: [RFC 1/6] migration: skipped field is really obsolete. |
Date: |
Thu, 22 Jun 2023 19:49:47 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) |
Daniel P. Berrangé <berrange@redhat.com> wrote:
> On Mon, Jun 12, 2023 at 09:33:39PM +0200, Juan Quintela wrote:
>> Has return zero for more than 10 years. Just mark it deprecated.
>
> Specifically we introduced the field in 1.5.0
>
> commit f1c72795af573b24a7da5eb52375c9aba8a37972
> Author: Peter Lieven <pl@kamp.de>
> Date: Tue Mar 26 10:58:37 2013 +0100
>
> migration: do not sent zero pages in bulk stage
>
> during bulk stage of ram migration if a page is a
> zero page do not send it at all.
> the memory at the destination reads as zero anyway.
>
> even if there is an madvise with QEMU_MADV_DONTNEED
> at the target upon receipt of a zero page I have observed
> that the target starts swapping if the memory is overcommitted.
> it seems that the pages are dropped asynchronously.
>
> this patch also updates QMP to return the number of
> skipped pages in MigrationStats.
>
>
>
> but removed its usage in 1.5.3
>
> commit 9ef051e5536b6368a1076046ec6c4ec4ac12b5c6
> Author: Peter Lieven <pl@kamp.de>
> Date: Mon Jun 10 12:14:19 2013 +0200
>
> Revert "migration: do not sent zero pages in bulk stage"
>
> Not sending zero pages breaks migration if a page is zero
> at the source but not at the destination. This can e.g. happen
> if different BIOS versions are used at source and destination.
> It has also been reported that migration on pseries is completely
> broken with this patch.
>
> This effectively reverts commit f1c72795af573b24a7da5eb52375c9aba8a37972.
Thanks for the history O:-)
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> ---
>> docs/about/deprecated.rst | 10 ++++++++++
>> qapi/migration.json | 12 ++++++++++--
>> 2 files changed, 20 insertions(+), 2 deletions(-)
>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>
>
>> diff --git a/qapi/migration.json b/qapi/migration.json
>> index cb7cd3e578..bcae193733 100644
>> --- a/qapi/migration.json
>> +++ b/qapi/migration.json
>> @@ -23,7 +23,8 @@
>> #
>> # @duplicate: number of duplicate (zero) pages (since 1.2)
>> #
>> -# @skipped: number of skipped zero pages (since 1.5)
>> +# @skipped: number of skipped zero pages. Don't use, only provided for
>> +# compatibility (since 1.5)
>
> I'd say
>
> @skipped: number of skipped zero pages. Always zero, only provided for
> compatibility (since 1.5)
Changed.
>> #
>> # @normal: number of normal pages (since 1.2)
>> #
>> @@ -62,11 +63,18 @@
>> # between 0 and @dirty-sync-count * @multifd-channels. (since
>> # 7.1)
>> #
>> +# Features:
>> +#
>> +# @deprecated: Member @skipped has not been used for a long time.
>
> @deprecated: Member @skipped is always zero since 1.5.3
Changed.
Thanks.
- [RFC 0/6] Migration deprecated parts, Juan Quintela, 2023/06/12
- [RFC 1/6] migration: skipped field is really obsolete., Juan Quintela, 2023/06/12
- [RFC 2/6] migration: migrate 'inc' command option is deprecated., Juan Quintela, 2023/06/12
- [RFC 3/6] migration: migrate 'blk' command option is deprecated., Juan Quintela, 2023/06/12
- [RFC 5/6] migration: Deprecate block migration, Juan Quintela, 2023/06/12
- [RFC 4/6] migration: Deprecate -incoming <uri>, Juan Quintela, 2023/06/12