Re: [Qemu-devel] [PATCH 09/10] migration: Make xbzrle_cache_size a migration parameter

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> Right now it is a variable in MigrationState instead of a
> MigrationParameter.  The change allows to set it as the rest of the
> Migration parameters, from the command line, with
> query_migration_paramters, set_migrate_parameters, etc.
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> ---
>  hmp.c                 | 14 ++++++++++++++
>  migration/migration.c | 39 ++++++++++++++++++++++++++++++---------
>  migration/migration.h |  1 -
>  migration/ram.c       |  7 -------
>  qapi/migration.json   | 23 ++++++++++++++++++++---
>  5 files changed, 64 insertions(+), 20 deletions(-)
> 
> diff --git a/hmp.c b/hmp.c
> index 739d330f4e..f73232399a 100644
> --- a/hmp.c
> +++ b/hmp.c
> @@ -342,6 +342,9 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict *qdict)
>          monitor_printf(mon, "%s: %" PRId64 "\n",
>              MigrationParameter_str(MIGRATION_PARAMETER_X_MULTIFD_PAGE_COUNT),
>              params->x_multifd_page_count);
> +        monitor_printf(mon, "%s: %" PRId64 "\n",
> +            MigrationParameter_str(MIGRATION_PARAMETER_XBZRLE_CACHE_SIZE),
> +            params->xbzrle_cache_size);
>      }
>  
>      qapi_free_MigrationParameters(params);
> @@ -1560,6 +1563,7 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict)
>      Visitor *v = string_input_visitor_new(valuestr);
>      MigrateSetParameters *p = g_new0(MigrateSetParameters, 1);
>      uint64_t valuebw = 0;
> +    uint64_t cache_size;
>      Error *err = NULL;
>      int val, ret;
>  
> @@ -1635,6 +1639,16 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict *qdict)
>          p->has_x_multifd_page_count = true;
>          visit_type_int(v, param, &p->x_multifd_page_count, &err);
>          break;
> +    case MIGRATION_PARAMETER_XBZRLE_CACHE_SIZE:
> +        p->has_xbzrle_cache_size = true;
> +        visit_type_size(v, param, &cache_size, &err);
> +        if (err || cache_size > INT64_MAX
> +            || (size_t)cache_size != cache_size) {
> +            error_setg(&err, "Invalid size %s", valuestr);
> +            break;
> +        }
> +        p->xbzrle_cache_size = cache_size;
> +        break;
>      default:
>          assert(0);
>      }
> diff --git a/migration/migration.c b/migration/migration.c
> index f3d4503ce2..fcc0d64625 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -71,7 +71,7 @@
>  #define DEFAULT_MIGRATE_CPU_THROTTLE_INCREMENT 10
>  
>  /* Migration XBZRLE default cache size */
> -#define DEFAULT_MIGRATE_CACHE_SIZE (64 * 1024 * 1024)
> +#define DEFAULT_MIGRATE_XBZRLE_CACHE_SIZE (64 * 1024 * 1024)
>  
>  /* The delay time (in ms) between two COLO checkpoints
>   * Note: Please change this default value to 10000 when we support hybrid mode.
> @@ -512,6 +512,8 @@ MigrationParameters *qmp_query_migrate_parameters(Error **errp)
>      params->x_multifd_channels = s->parameters.x_multifd_channels;
>      params->has_x_multifd_page_count = true;
>      params->x_multifd_page_count = s->parameters.x_multifd_page_count;
> +    params->has_xbzrle_cache_size = true;
> +    params->xbzrle_cache_size = s->parameters.xbzrle_cache_size;
>  
>      return params;
>  }
> @@ -810,6 +812,16 @@ static bool migrate_params_check(MigrationParameters *params, Error **errp)
>          return false;
>      }
>  
> +    if (params->has_xbzrle_cache_size &&
> +        (params->xbzrle_cache_size < qemu_target_page_size() ||
> +         !is_power_of_2(params->xbzrle_cache_size))) {
> +        error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
> +                   "xbzrle_cache_size",
> +                   "is invalid, it should be bigger than target page size"
> +                   " and a power of two");
> +        return false;
> +    }
> +
>      return true;
>  }
>  
> @@ -871,6 +883,9 @@ static void migrate_params_test_apply(MigrateSetParameters *params,
>      if (params->has_x_multifd_page_count) {
>          dest->x_multifd_page_count = params->x_multifd_page_count;
>      }
> +    if (params->has_xbzrle_cache_size) {
> +        dest->xbzrle_cache_size = params->xbzrle_cache_size;
> +    }
>  }
>  
>  static void migrate_params_apply(MigrateSetParameters *params)
> @@ -939,6 +954,10 @@ static void migrate_params_apply(MigrateSetParameters *params)
>      if (params->has_x_multifd_page_count) {
>          s->parameters.x_multifd_page_count = params->x_multifd_page_count;
>      }
> +    if (params->has_xbzrle_cache_size) {
> +        s->parameters.xbzrle_cache_size = params->xbzrle_cache_size;
> +        xbzrle_cache_resize(params->xbzrle_cache_size, NULL);

Not having the errp is a pain;   you've just moved all the error
checking into xbzrle_cache_resize, so I think we really need an error
pointer and to do something with it (even if it's just a local report).

> +    }
>  }
>  
>  void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
> @@ -1370,13 +1389,12 @@ void qmp_migrate_cancel(Error **errp)
>  
>  void qmp_migrate_set_cache_size(int64_t value, Error **errp)
>  {
> -    MigrationState *s = migrate_get_current();
> +    MigrateSetParameters p = {
> +        .has_xbzrle_cache_size = true,
> +        .xbzrle_cache_size = value,
> +    };
>  
> -    if (xbzrle_cache_resize(value, errp) < 0) {
> -        return;
> -    }
> -
> -    s->xbzrle_cache_size = value;
> +    qmp_migrate_set_parameters(&p, errp);
>  }
>  
>  int64_t qmp_query_migrate_cache_size(Error **errp)
> @@ -1542,7 +1560,7 @@ int64_t migrate_xbzrle_cache_size(void)
>  
>      s = migrate_get_current();
>  
> -    return s->xbzrle_cache_size;
> +    return s->parameters.xbzrle_cache_size;
>  }
>  
>  bool migrate_use_block(void)
> @@ -2312,6 +2330,9 @@ static Property migration_properties[] = {
>      DEFINE_PROP_INT64("x-multifd-page-count", MigrationState,
>                        parameters.x_multifd_page_count,
>                        DEFAULT_MIGRATE_MULTIFD_PAGE_COUNT),
> +    DEFINE_PROP_SIZE("xbzrle-cache-size", MigrationState,
> +                      parameters.xbzrle_cache_size,
> +                      DEFAULT_MIGRATE_XBZRLE_CACHE_SIZE),
>  
>      /* Migration capabilities */
>      DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
> @@ -2353,7 +2374,6 @@ static void migration_instance_init(Object *obj)
>      MigrationParameters *params = &ms->parameters;
>  
>      ms->state = MIGRATION_STATUS_NONE;
> -    ms->xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE;
>      ms->mbps = -1;
>  
>      params->tls_hostname = g_strdup("");
> @@ -2371,6 +2391,7 @@ static void migration_instance_init(Object *obj)
>      params->has_block_incremental = true;
>      params->has_x_multifd_channels = true;
>      params->has_x_multifd_page_count = true;
> +    params->has_xbzrle_cache_size = true;
>  }
>  
>  /*
> diff --git a/migration/migration.h b/migration/migration.h
> index b83cceadc4..d2a8d319f1 100644
> --- a/migration/migration.h
> +++ b/migration/migration.h
> @@ -107,7 +107,6 @@ struct MigrationState
>      int64_t downtime;
>      int64_t expected_downtime;
>      bool enabled_capabilities[MIGRATION_CAPABILITY__MAX];
> -    int64_t xbzrle_cache_size;
>      int64_t setup_time;
>  
>      /* Flag set once the migration has been asked to enter postcopy */
> diff --git a/migration/ram.c b/migration/ram.c
> index ed4d3c6295..78e3b80e39 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -128,13 +128,6 @@ int xbzrle_cache_resize(int64_t new_size, Error **errp)
>          return -1;
>      }
>  
> -    /* Cache should not be larger than guest ram size */
> -    if (new_size > ram_bytes_total()) {
> -        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
> -                   "exceeds guest ram size");
> -        return -1;
> -    }
> -
>      if (new_size == migrate_xbzrle_cache_size()) {
>          /* nothing to do */
>          return new_size;
> diff --git a/qapi/migration.json b/qapi/migration.json
> index f8b365e3f5..830b2e4480 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -474,6 +474,10 @@
>  # @x-multifd-page-count: Number of pages sent together to a thread
>  #                        The default value is 16 (since 2.11)
>  #
> +# @xbzrle-cache-size: cache size to be used by XBZRLE migration.  It
> +#                     needs to be a multiple of the target page size

and power of 2

> +#                     (Since 2.11)
> +#
>  # Since: 2.4
>  ##
>  { 'enum': 'MigrationParameter',
> @@ -481,7 +485,8 @@
>             'cpu-throttle-initial', 'cpu-throttle-increment',
>             'tls-creds', 'tls-hostname', 'max-bandwidth',
>             'downtime-limit', 'x-checkpoint-delay', 'block-incremental',
> -           'x-multifd-channels', 'x-multifd-page-count' ] }
> +           'x-multifd-channels', 'x-multifd-page-count',
> +           'xbzrle-cache-size' ] }
>  
>  ##
>  # @MigrateSetParameters:
> @@ -545,6 +550,9 @@
>  # @x-multifd-page-count: Number of pages sent together to a thread
>  #                        The default value is 16 (since 2.11)
>  #
> +# @xbzrle-cache-size: cache size to be used by XBZRLE migration.  It
> +#                     needs to be a multiple of the target page size
> +#                     (Since 2.11)

and power of 2

>  # Since: 2.4
>  ##
>  # TODO either fuse back into MigrationParameters, or make
> @@ -562,7 +570,8 @@
>              '*x-checkpoint-delay': 'int',
>              '*block-incremental': 'bool',
>              '*x-multifd-channels': 'int',
> -            '*x-multifd-page-count': 'int' } }
> +            '*x-multifd-page-count': 'int',
> +            '*xbzrle-cache-size': 'size' } }
>  
>  ##
>  # @migrate-set-parameters:
> @@ -641,6 +650,9 @@
>  # @x-multifd-page-count: Number of pages sent together to a thread
>  #                        The default value is 16 (since 2.11)
>  #
> +# @xbzrle-cache-size: cache size to be used by XBZRLE migration.  It
> +#                     needs to be a multiple of the target page size
> +#                     (Since 2.11)

and power of 2 (wow this text is repeated a lot)

>  # Since: 2.4
>  ##
>  { 'struct': 'MigrationParameters',
> @@ -656,7 +668,8 @@
>              '*x-checkpoint-delay': 'int',
>              '*block-incremental': 'bool' ,
>              '*x-multifd-channels': 'int',
> -            '*x-multifd-page-count': 'int' } }
> +            '*x-multifd-page-count': 'int',
> +            '*xbzrle-cache-size': 'size' } }
>  
>  ##
>  # @query-migrate-parameters:
> @@ -921,6 +934,8 @@
>  #
>  # Returns: nothing on success
>  #
> +# Notes: This command is deprecated in favor of 'migrate-set-parameters'
> +#
>  # Since: 1.2
>  #
>  # Example:
> @@ -939,6 +954,8 @@
>  #
>  # Returns: XBZRLE cache size in bytes
>  #
> +# Notes: This command is deprecated in favor of 'query-migrate-parameters'
> +#
>  # Since: 1.2
>  #
>  # Example:
> -- 
> 2.13.6

Dave

> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK