Re: [PATCH v3 01/20] multifd: Add capability to enable/disable zero_page

[Fabiano Rosas <farosas@suse.de>]

Hao Xiang <hao.xiang@bytedance.com> writes:

> From: Juan Quintela <quintela@redhat.com>
>
> We have to enable it by default until we introduce the new code.
>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/options.c | 15 +++++++++++++++
>  migration/options.h |  1 +
>  qapi/migration.json |  8 +++++++-
>  3 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/migration/options.c b/migration/options.c
> index 8d8ec73ad9..0f6bd78b9f 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -204,6 +204,8 @@ Property migration_properties[] = {
>      DEFINE_PROP_MIG_CAP("x-switchover-ack",
>                          MIGRATION_CAPABILITY_SWITCHOVER_ACK),
>      DEFINE_PROP_MIG_CAP("x-dirty-limit", MIGRATION_CAPABILITY_DIRTY_LIMIT),
> +    DEFINE_PROP_MIG_CAP("main-zero-page",
> +            MIGRATION_CAPABILITY_MAIN_ZERO_PAGE),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> @@ -284,6 +286,19 @@ bool migrate_multifd(void)
>      return s->capabilities[MIGRATION_CAPABILITY_MULTIFD];
>  }
>  
> +bool migrate_use_main_zero_page(void)
> +{
> +    /* MigrationState *s; */
> +
> +    /* s = migrate_get_current(); */
> +
> +    /*
> +     * We will enable this when we add the right code.
> +     * return s->enabled_capabilities[MIGRATION_CAPABILITY_MAIN_ZERO_PAGE];
> +     */
> +    return true;
> +}
> +
>  bool migrate_pause_before_switchover(void)
>  {
>      MigrationState *s = migrate_get_current();
> diff --git a/migration/options.h b/migration/options.h
> index 246c160aee..c901eb57c6 100644
> --- a/migration/options.h
> +++ b/migration/options.h
> @@ -88,6 +88,7 @@ int migrate_multifd_channels(void);
>  MultiFDCompression migrate_multifd_compression(void);
>  int migrate_multifd_zlib_level(void);
>  int migrate_multifd_zstd_level(void);
> +bool migrate_use_main_zero_page(void);
>  uint8_t migrate_throttle_trigger_threshold(void);
>  const char *migrate_tls_authz(void);
>  const char *migrate_tls_creds(void);
> diff --git a/qapi/migration.json b/qapi/migration.json
> index eb2f883513..80c4b13516 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -531,6 +531,12 @@
>  #     and can result in more stable read performance.  Requires KVM
>  #     with accelerator property "dirty-ring-size" set.  (Since 8.1)
>  #
> +#
> +# @main-zero-page: If enabled, the detection of zero pages will be
> +#                  done on the main thread.  Otherwise it is done on
> +#                  the multifd threads.
> +#                  (since 8.2)
> +#
>  # Features:
>  #
>  # @deprecated: Member @block is deprecated.  Use blockdev-mirror with
> @@ -555,7 +561,7 @@
>             { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
>             'validate-uuid', 'background-snapshot',
>             'zero-copy-send', 'postcopy-preempt', 'switchover-ack',
> -           'dirty-limit'] }
> +           'dirty-limit', 'main-zero-page'] }
>  
>  ##
>  # @MigrationCapabilityStatus:

I'll extract this zero page work into a separate series and submit for
review soon. I want to get people's opinion on it independently of this
series.