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

[Zheng Chuan]

On 2020/9/28 20:23, David Edmondson wrote:
> 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.
> 
Hi, David.
Yes, maybe we should record start-time and calc-time in reset_dirtyrate_stat() 
and move it forward just after
setting CalculatingState status succeed in get_dirtyrate_thread.

>> @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.
> 
That's better, thanks.

>>  #
>>  # @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.
>