Re: [PATCH 1/5] multifd: Create property multifd-sync-each-iteration

[Dr. David Alan Gilbert]

* Juan Quintela (quintela@redhat.com) wrote:
> We used to synchronize all channels at the end of each RAM section
> sent.  That is not needed, so preparing to only synchronize once every
> full round in latests patches.
> 
> Notice that we initialize the property as true.  We will change the
> default when we introduce the new mechanism.

I don't understand why this is a property - does it break the actual
stream format?

Dave

> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  migration/migration.h |  6 ++++++
>  hw/core/machine.c     |  1 +
>  migration/migration.c | 10 ++++++++++
>  3 files changed, 17 insertions(+)
> 
> diff --git a/migration/migration.h b/migration/migration.h
> index 485d58b95f..70dae24516 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -332,6 +332,11 @@ struct MigrationState {
>       * This save hostname when out-going migration starts
>       */
>      char *hostname;
> +    /*
> +     * Synchronize channels after each iteration.
> +     * We used to do that on the past, but it is suboptimal.
> +     */
> +    bool multifd_sync_each_iteration;
>  };
>  
>  void migrate_set_state(int *state, int old_state, int new_state);
> @@ -374,6 +379,7 @@ int migrate_multifd_channels(void);
>  MultiFDCompression migrate_multifd_compression(void);
>  int migrate_multifd_zlib_level(void);
>  int migrate_multifd_zstd_level(void);
> +bool migrate_multifd_sync_each_iteration(void);
>  
>  #ifdef CONFIG_LINUX
>  bool migrate_use_zero_copy_send(void);
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index a673302cce..c8a60917e0 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -43,6 +43,7 @@
>  GlobalProperty hw_compat_7_0[] = {
>      { "arm-gicv3-common", "force-8-bit-prio", "on" },
>      { "nvme-ns", "eui64-default", "on"},
> +    { "migration", "multifd-sync-each-iteration", "on"},
>  };
>  const size_t hw_compat_7_0_len = G_N_ELEMENTS(hw_compat_7_0);
>  
> diff --git a/migration/migration.c b/migration/migration.c
> index 31739b2af9..3f79df0b70 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2540,6 +2540,13 @@ bool migrate_use_multifd(void)
>      return s->enabled_capabilities[MIGRATION_CAPABILITY_MULTIFD];
>  }
>  
> +bool migrate_multifd_sync_each_iteration(void)
> +{
> +    MigrationState *s = migrate_get_current();
> +
> +    return s->multifd_sync_each_iteration;
> +}
> +
>  bool migrate_pause_before_switchover(void)
>  {
>      MigrationState *s;
> @@ -4274,6 +4281,9 @@ static Property migration_properties[] = {
>      DEFINE_PROP_SIZE("announce-step", MigrationState,
>                        parameters.announce_step,
>                        DEFAULT_MIGRATE_ANNOUNCE_STEP),
> +    /* We will change to false when we introduce the new mechanism */
> +    DEFINE_PROP_BOOL("multifd-sync-each-iteration", MigrationState,
> +                      multifd_sync_each_iteration, true),
>  
>      /* Migration capabilities */
>      DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
> -- 
> 2.34.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK