~hyman <hy...@git.sr.ht> writes:
> From: Hyman Huang(黄勇) <yong.hu...@smartx.com>
>
> Introduce migration dirty-limit capability, which can
> be turned on before live migration and limit dirty
> page rate durty live migration.
>
> Introduce migrate_dirty_limit function to help check
> if dirty-limit capability enabled during live migration.
>
> Meanwhile, refactor vcpu_dirty_rate_stat_collect
> so that period can be configured instead of hardcoded.
>
> dirty-limit capability is kind of like auto-converge
> but using dirty limit instead of traditional cpu-throttle
> to throttle guest down. To enable this feature, turn on
> the dirty-limit capability before live migration using
> migrate-set-capabilities, and set the parameters
> "x-vcpu-dirty-limit-period", "vcpu-dirty-limit" suitably
> to speed up convergence.
>
> Signed-off-by: Hyman Huang(黄勇) <yong.hu...@smartx.com>
> Acked-by: Peter Xu <pet...@redhat.com>
> Reviewed-by: Juan Quintela <quint...@redhat.com>
[...]
> diff --git a/migration/options.h b/migration/options.h
> index 9aaf363322..b5a950d4e4 100644
> --- a/migration/options.h
> +++ b/migration/options.h
> @@ -24,6 +24,7 @@ extern Property migration_properties[];
> /* capabilities */
>
> bool migrate_auto_converge(void);
> +bool migrate_dirty_limit(void);
> bool migrate_background_snapshot(void);
> bool migrate_block(void);
> bool migrate_colo(void);
> diff --git a/qapi/migration.json b/qapi/migration.json
> index aa590dbf0e..cc51835cdd 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -497,6 +497,16 @@
> # are present. 'return-path' capability must be enabled to use
> # it. (since 8.1)
> #
> +# @dirty-limit: If enabled, migration will use the dirty-limit algo to
> +# throttle down guest instead of auto-converge algo.
> +# Throttle algo only works when vCPU's dirtyrate greater
> +# than 'vcpu-dirty-limit', read processes in guest os
> +# aren't penalized any more, so this algo can improve
> +# performance of vCPU during live migration. This is an
> +# optional performance feature and should not affect the
> +# correctness of the existing auto-converge algo.
> +# (since 8.1)
> +#
Please format like
# @dirty-limit: If enabled, migration will use the dirty-limit algo to
# throttle down guest instead of auto-converge algo. Throttle
# algo only works when vCPU's dirtyrate greater than
# 'vcpu-dirty-limit', read processes in guest os aren't penalized
# any more, so this algo can improve performance of vCPU during
# live migration. This is an optional performance feature and
# should not affect the correctness of the existing auto-converge
# algo. (since 8.1)
to blend in with recent commit a937b6aa739 (qapi: Reformat doc comments
to conform to current conventions).
"Dirty rate" with a space, because that's how we spell it elsewhere.
Moreover, "algo" is not a word, "algorithm" is :)
Is "the dirty-limit algorithm" defined anywhere?
More word-smithing is needed, but I'd like to get the reference to "the
dirty-limit algorithm" clarified first.
> # Features:
> #
> # @unstable: Members @x-colo and @x-ignore-shared are experimental.
> @@ -512,7 +522,8 @@
> 'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
> { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
> 'validate-uuid', 'background-snapshot',
> - 'zero-copy-send', 'postcopy-preempt', 'switchover-ack'] }
> + 'zero-copy-send', 'postcopy-preempt', 'switchover-ack',
> + 'dirty-limit'] }
>
> ##
> # @MigrationCapabilityStatus:
[...]
