Re: [PATCH v2] migration/throttle: Add cpu-throttle-tailslow migration parameter

[zhukeqian]

Hi Eric,

On 2020/3/31 23:03, Eric Blake wrote:
> On 3/15/20 11:29 PM, Keqian Zhu wrote:
>> At the tail stage of throttling, the Guest is very sensitive to
>> CPU percentage while the @cpu-throttle-increment is excessive
>> usually at tail stage.
>>
>> If this parameter is true, we will compute the ideal CPU percentage
>> used by the Guest, which may exactly makes dirty rate to be dirty
>> rate threshold. Then we will choose a smaller throttle increment
>> between the one specified by @cpu-throttle-increment and the one
>> generated by ideal CPU percentage.
>>
>> Therefore, it is compatible to traditional throttling, meanwhile
>> the throttle increment won't be excessive at tail stage. This may
>> make migration time longer, and is disabled by default.
>>
>> 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
>> @@ -552,6 +552,21 @@
>>   #                          auto-converge detects that migration is not 
>> making
>>   #                          progress. The default value is 10. (Since 2.7)
>>   #
>> +# @cpu-throttle-tailslow: Make CPU throttling slower at tail stage
>> +#                         At the tail stage of throttling, the Guest is very
>> +#                         sensitive to CPU percentage while the 
>> @cpu-throttle
>> +#                         -increment is excessive usually at tail stage.
>> +#                         If this parameter is true, we will compute the 
>> ideal
>> +#                         CPU percentage used by the Guest, which may 
>> exactly
>> +#                         makes dirty rate to be dirty rate threshold. Then 
>> we
> 
> Grammar is off here, but I don't know if you meant "which may exactly make 
> the dirty rate match the dirty rate threshold" or something else.
> 
yep, this is what I want to express. I will correct it in v3. Thanks.
>> +#                         will choose a smaller throttle increment between 
>> the
>> +#                         one specified by @cpu-throttle-increment and the 
>> one
>> +#                         generated by ideal CPU percentage.
>> +#                         Therefore, it is compatible to traditional 
>> throttling,
>> +#                         meanwhile the throttle increment won't be 
>> excessive
>> +#                         at tail stage.
>> +#                         The default value is false. (Since 5.0)
> 
> Is this a bug-fix that must make it into 5.0?  It seems more like a feature 
> addition, at which point listing it for 5.1 is probably a better idea.
> 
Thanks for figuring it out.
This patch is sent out when v5.0 is not released.
I will correct it in v3.

Thanks,
Keqian