Re: [Qemu-devel] Migration ToDo list

[Isaku Yamahata <yamahata@valinux.co.jp>]

On Tue, Nov 13, 2012 at 06:16:30PM +0100, Paolo Bonzini wrote:
> Il 13/11/2012 18:09, Orit Wasserman ha scritto:
> >> > 
> >>> >>   b) do scatter/gather of the pages?
> > I would prefer to postpone changing the protocol and start with using iov (writev)
> > for sending the pages (still sending header and than the page). Later we can 
> > move to scatter/gather I'm not sure of how large the performance gain will be.
> >> > 
> >> > c) Remove compression of non-zero repetitive pages.
> > +1
> > we can look of identify the zero pages without calling is_dup_page which looks
> > expensive.
> 
> Identifying ballooned zero pages is useful, because those cause the
> clear_page calls in the kernel even in a guest that has been running for
> a while.
> 
> But a generic solution doesn't really matter, because is_dup_page and
> clear_page shouldn't really be in the profile in practice, except in
> microbenchmarks.

I guess mincore(2) can be used as easy way to detect non-mapped page.
This is just implementation detail anyway.
-- 
yamahata