Re: [PATCH] migration/dirtyrate: present dirty rate only when querying the rate has completed

[David Edmondson]

On Sunday, 2020-09-27 at 12:55:20 +08, Chuan Zheng wrote:

> Make dirty_rate field optional, present dirty rate only when querying
> the rate has completed.
> The qmp results is shown as follow:
> @unstarted:
> {"return":{"status":"unstarted","start-time":0,"calc-time":0},"id":"libvirt-12"}
> @measuring:
> {"return":{"status":"measuring","start-time":0,"calc-time":0},"id":"libvirt-14"}

Not this patch, but the "measuring" state could include both the
start-time and the calc-time, allowing a caller to determine when they
should expect to come back looking for a result.

> @measured:
> {"return":{"status":"measured","dirty-rate":4,"start-time":150146,"calc-time":1},"id":"libvirt-15"}
>
> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>

With the minor wording changes below...

Reviewed-by: David Edmondson <david.edmondson@oracle.com>

> ---
>  migration/dirtyrate.c | 3 +--
>  qapi/migration.json   | 9 ++++-----
>  2 files changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
> index 68577ef..9024b0f 100644
> --- a/migration/dirtyrate.c
> +++ b/migration/dirtyrate.c
> @@ -69,9 +69,8 @@ static struct DirtyRateInfo *query_dirty_rate_info(void)
>      struct DirtyRateInfo *info = g_malloc0(sizeof(DirtyRateInfo));
>  
>      if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURED) {
> +        info->has_dirty_rate = true;
>          info->dirty_rate = dirty_rate;
> -    } else {
> -        info->dirty_rate = -1;
>      }
>  
>      info->status = CalculatingState;
> diff --git a/qapi/migration.json b/qapi/migration.json
> index ce2216c..6e428f7 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1743,10 +1743,9 @@
>  #
>  # Information about current dirty page rate of vm.
>  #
> -# @dirty-rate: @dirtyrate describing the dirty page rate of vm
> -#          in units of MB/s.
> -#          If this field returns '-1', it means querying has not
> -#          yet started or completed.
> +# @dirty-rate: dirty-rate describing the dirty page rate of vm
> +#              in units of MB/s, present only when querying the
> +#              rate has completed.

How about:

@dirty-rate: an estimate of the dirty page rate of the VM in units of
             MB/s, present only when estimating the rate has completed.

>  #
>  # @status: status containing dirtyrate query status includes
>  #          'unstarted' or 'measuring' or 'measured'
> @@ -1759,7 +1758,7 @@
>  #
>  ##
>  { 'struct': 'DirtyRateInfo',
> -  'data': {'dirty-rate': 'int64',
> +  'data': {'*dirty-rate': 'int64',
>             'status': 'DirtyRateStatus',
>             'start-time': 'int64',
>             'calc-time': 'int64'} }
> -- 
> 1.8.3.1

dme.
-- 
I used to worry, thought I was goin' mad in a hurry.