Re: kvm userspace: ksm support

[Anthony Liguori <anthony@codemonkey.ws>]

Izik Eidus wrote:
>
> You mean: when we later call for other madvise calls, if it will 
> remove the MADV_MERGEABLE from that memory?
> if yes, the answer is no, it should be still l left in the 
> vma->vm_flags...

Excellent.

>>
>> I'd suggest doing the following in osdep.h too:
>>
>> #if !defined(MADV_MERGABLE)
>> #define MADV_MERGABLE MADV_NORMAL
>> #endif
>>
>> To avoid #ifdefs in .c files.
>
> I tried to follow the way DONTFORK madvise is working...
>
> So you say, just to throw this thing into osdep.h instead of that c file?

Yes.

I think the DONTFORK thing is a bit odd.  Of course we have 
MADV_DONTFORK if we're running KVM.  I'm not sure why that is there.

I also think that we could get away with getting rid of any checks for 
!sync_mmu() since that was introduced in 2.6.27.

Otherwise, you should technically avoid doing madvise() unless we have 
sync_mmu().

Regards,

Anthony Liguori