Re: [Qemu-devel] [RFC] parallelize migration_bitmap_sync()

[Michael R. Hines]

Oh, that's fantastic - thanks for the response.

- Michael

On 03/01/2013 04:34 AM, Paolo Bonzini wrote:
> Il 01/03/2013 00:22, Michael R. Hines ha scritto:te
> > Hi,
> >
> > Currently migration_bitmap_sync() is very expensive: on the order of
> > 15-20 milliseconds by my count using timestamps (for a simple 2GB ram
> > virtual machine).
> > Until new EPT processor versions come out in 2014, we need software
> > support for cutting this time down much lower........by at least an
> > order of magnitude.
> >
> > Would anyone be opposed to me writing a patch that creates N threads and
> > dividing up the migration_bitmap_sync() function to have the dirty page
> > scanning run in parallel?
> Yes, that's a possibility.  You can make a quick prototype using OpenMP.
>
> But Juan is working on making the dirty bitmap really a bitmap (not a
> "bytemap").  That should speed up migration_bitmap_sync by a factor of
> 64 (i.e. sizeof(long)*8).
>
> Paolo