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

[Paolo Bonzini]

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