Re: [Qemu-devel] [PATCH v3 3/5] migration: Dynamic cpu throttling for auto-converge

["Jason J. Herne" <jjherne@linux.vnet.ibm.com>]

On 06/26/2015 01:54 PM, Dr. David Alan Gilbert wrote:
> * Jason J. Herne (jjherne@linux.vnet.ibm.com) wrote:
...
>> diff --git a/migration/migration.c b/migration/migration.c
>> index 05790e9..7708c54 100644
>> --- a/migration/migration.c
>> +++ b/migration/migration.c
>> @@ -25,6 +25,7 @@
>>   #include "qemu/thread.h"
>>   #include "qmp-commands.h"
>>   #include "trace.h"
>> +#include "qom/cpu.h"
>>
>>   #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */
>>
>> @@ -858,6 +859,9 @@ static void *migration_thread(void *opaque)
>>           }
>>       }
>>
>> +    /* If we enabled cpu throttling for auto-converge, turn it off. */
>> +    cpu_throttle_stop();
>> +
>>       qemu_mutex_lock_iothread();
>>       if (s->state == MIGRATION_STATUS_COMPLETED) {
>>           int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>
> Is that cpu_throttle_stop() sufficient if I use 'migration cancel'
> so that next time through it's all reset so that there's no throttling
> at the beginning?
>

It will be reset when cpu_throttle_set is called again when auto-converge
re-enables throttling for the next migration. This happens in patch 3,
mig_throttle_guest_down():

Basically, cpu_throttle_set requires the user to provide a throttling
percentage. So starting a new throttling operation will overwrite the
previous value.

-- 
-- Jason J. Herne (jjherne@linux.vnet.ibm.com)