Re: Resend: patch: qemu + hugetlbfs..

[john cooper <john.cooper@redhat.com>]

Avi Kivity wrote:
> john cooper wrote:
>> This patch from over a month ago doesn't seem to have
>> made it into kvm-73 and may have been lost in the
>> shuffle.  Attached is essentially the same patch but
>> as applied to kvm-73, and validated relative to that
>> version.
>>
>
> What is the motivation for providing an option to disable this?  If we 
> can detect mem-path is backed by huge pages somehow, I think we can 
> prefault the memory unconditionally.
>
Pre-allocation of the entire huge page backed guest
memory avoids the nondeterministic termination but
admittedly is overly pessimistic.  As this patch does
so by default when -mem-path is specified, allowing
for disable of pre-allocation simply reverts this
change to prior behavior for use cases more tolerant
to it as well as for debug purposes.

The real fix arguably hinges on huge pages having
more general virtual memory behavior.  But that
appears to be a much longer term prospect.

-john

-- 
john.cooper@redhat.com