Re: [Qemu-devel] [PATCH V2] add migration capability to bypass the shared memory

[Li, Liang Z]

> >>
> >> I might have missed something, could you tell me more?
> >>
> >> void bitmap_set(unsigned long *map, long start, long nr); I think the
> >> @start and @nr are both the number of the bits.
> >>
> >> thanks,
> >> Lai
> >
> > You are right,  I have make a mistake by checking the code. Sorry for the
> noise.
> >
> > BTW. Is it possible to bypass the shared block in the
> 'ram_find_and_save_block'?
> > I mean no to check if a page is dirty for a shared block, it may make things
> faster.
> 
> Nice spotted.  That would make things faster.  But once there we could split
> the bitmap by ramblock, and the migration_dirty_pages also per block, that
> would make all the searchs faster, and adding/removing blocks of ram much
> easier.  If we enter optimizing that function, we could really do much better
> that the "again" parameter that we have right now.
> 
> Later, Juan.

Did some experiment with an 8GB VM.
Total time: 93ms
Setup: 70ms
Downtime: 6ms

So most of the time spend on Setup stage, and most of the time spend on 
setup stage is starting dirty page logging.
How about not start dirty page logging for shared blocks? then it's possible
to shorten the total time to about 30ms.

Liang