Re: [Qemu-devel] Migration ToDo list

[Paolo Bonzini]

Il 14/11/2012 03:14, Isaku Yamahata ha scritto:
>> > 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.

Doesn't work if the page is swapped, doesn't it?

But I wonder if the clear_page occurrences are because of the problem
described recently on LWN (http://lwn.net/Articles/517465/), and so
really more of a kernel bug than anything else.

Paolo