Re: [Qemu-devel] [PATCH v12 00/21] Multifd

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Juan Quintela (quintela@redhat.com) wrote:
> Juan Quintela <quintela@redhat.com> wrote:
> > Hi
> >
> >
> > [v12]
> >
> > Big news, it is not RFC anymore, it works reliabely for me.
> >
> > Changes:
> > - Locknig changed completely (several times)
> > - We now send  all pages through the channels.  In a 2GB guest with 1 disk and a network card, the amount of data send for RAM was 80KB.
> > - This is not optimized yet, but it shouws clear improvements over precopy.  testing over localhost networking I can guet:
> >   - 2 VCPUs guest
> >   - 2GB RAM
> >   - runn stress --vm 4 --vm 500GB (i.e. dirtying 2GB or RAM each second)
> >
> >   - Total time: precopy ~50seconds, multifd  around 11seconds
> >   - Bandwidth usage is around 273MB/s vs 71MB/s on the same hardware
> >
> > This is very preleminary testing, will send more numbers when I got them.  But looks promissing.
> >
> > Things that will be improved later:
> > - Initial synchronization is too slow (around 1s)
> > - We synchronize all threads after each RAM section, we can move to only
> >   synchronize them after we have done a bitmap syncrhronization
> > - We can improve bitmap walking (but that is independent of multifd)
> 
> I forgot to put there that on the last 4 patches, I have not been able
> to split them in a way that:
> - is logical for review
> - works for multifd tests in all versions
> 
> So, I ended trynig to get the "logical" viewe, and it works after the
> last patch.  Why is that?
> - Before I am able to transmit data, I need to be able to
>   end/synchronize the different channels
> - To finish channels in case of error, I just close the channels
>   But I can't opet then yet.
> 
> I have to think if I can come with a simpler way to split it, but you
> can also consider that the  last 3-4 patches are a single one.

I think most of the last few can be flattened into earlier patches;
I'd prefer it rather than having patches that add stuff and then they
get reworked/removed later.

I don't think it matters that the order of the last few doesn't work
until the end; since it didn't work at the beginning, it doesn't matter
until the end of the series.

Dave

> Later, Juan.
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK