libvirt users - Mar 2014 - Re: [Qemu-devel] Adjust disk image migration (NBD)

On 24/02/14 23:26, Paolo Bonzini wrote:
>> Thanks for raising this.
>>
>> I noticed that mirror_run() does not throttle the first loop where it
>> populates the dirty bitmap using bdrv_is_allocated_above().
> This is on purpose.  Does it causes a noticeable stall in the guest?
>
>> The main
>> copy loop does take the speed limit into account but perhaps that's
>> broken too.
> Yeah, it looks broken.  Each iteration of the loop can write much more
> than sectors_per_chunk sectors, but here:
>
>              if (s->common.speed) {
>                  delay_ns = ratelimit_calculate_delay(&s->limit,
sectors_per_chunk);
>              } else {
>                  delay_ns = 0;
>              }
>
> the second argument is fixed. :/
>
> Paolo
>
Thanks for the answer. Something is still not clear to me. Are we in 
front of a bug (that means, something that could be fixed) or is this 
behaviour somehow expected for some reason? More and more tests I am 
doing, I get allways the same throughput chart: unlimited bandwidth when 
syncronizing the disk, and smooth bandwidth limit when migrating RAM.

Joaquim

Il 28/02/2014 11:41, Joaquim Barrera ha scritto:
>>
>
> Thanks for the answer. Something is still not clear to me. Are we in
> front of a bug (that means, something that could be fixed) or is this
> behaviour somehow expected for some reason? More and more tests I am
> doing, I get allways the same throughput chart: unlimited bandwidth when
> syncronizing the disk, and smooth bandwidth limit when migrating RAM.
>
> Joaquim
Yes, it's a bug that we can fix.

Paolo

On 28/02/14 11:43, Paolo Bonzini wrote:
> Il 28/02/2014 11:41, Joaquim Barrera ha scritto:
>>>
>>
>> Thanks for the answer. Something is still not clear to me. Are we in
>> front of a bug (that means, something that could be fixed) or is this
>> behaviour somehow expected for some reason? More and more tests I am
>> doing, I get allways the same throughput chart: unlimited bandwidth
when
>> syncronizing the disk, and smooth bandwidth limit when migrating RAM.
>>
>> Joaquim
>
> Yes, it's a bug that we can fix.
>
Hi Paolo et all. Can you tell me how to "start" the process of bug 
fixing? Am I supposed to report it somewhere, or did you just take note?

Thanks a lot.
> Paolo
>
>