Re: [PATCH] migration/throttle: Add throttle-trig-thres migration parameter

[zhukeqian]

Hi, Eric

On 2020/2/21 22:14, Eric Blake wrote:
> On 2/20/20 8:57 PM, Keqian Zhu wrote:
>> Currently, if the bytes_dirty_period is more than the 50% of
>> bytes_xfer_period, we start or increase throttling.
>>
>> If we make this percentage higher, then we can tolerate higher
>> dirty rate during migration, which means less impact on guest.
>> The side effect of higher percentage is longer migration time.
>>
>> We can configure this parameter to switch between migration time
>> firt or guest performance first. The default value is 50.
>>
>> Signed-off-by: Keqian Zhu <address@hidden>
>> ---
>> Cc: Juan Quintela <address@hidden>
>> Cc: "Dr. David Alan Gilbert" <address@hidden>
>> Cc: Eric Blake <address@hidden>
>> Cc: Markus Armbruster <address@hidden>
>> ---
> 
>> +++ b/qapi/migration.json
>> @@ -524,6 +524,10 @@
>>   #                      compression, so set the decompress-threads to the 
>> number about 1/4
>>   #                      of compress-threads is adequate.
>>   #
>> +# @throttle-trig-thres: The ratio of bytes_dirty_period and 
>> bytes_xfer_period to
>> +#                       trigger throttling. It is expressed as percentage. 
>> The
>> +#                       default value is 50. (Since 5.0)
>> +#
> 
> Abbreviating feels odd; can you please spell this out as 
> throttle-trigger-threshold?
OK, I will use full name in v2.
> 
> Can the threshold exceed 100%?
If the threshold exceed 100% and the dirty rate is between 100% and threshold, 
then throttling
will not be started, so the migration will not converge and last an uncertain 
time until the workload
in guest is down by itself. So I think that the threshold exceed 100% maybe not 
suitable :).
> 

Thanks.
Keqian