[PATCH V2 4/5] kvm/stats: Add provisioning for 64-bit vcpu statistics

[David Matlack]

On Mon, Jul 11, 2016 at 12:31 PM, Paolo Bonzini <pbonzini at redhat.com> wrote:
>
>
> On 11/07/2016 19:30, David Matlack wrote:
>> On Mon, Jul 11, 2016 at 10:05 AM, Paolo Bonzini <pbonzini at redhat.com> wrote:
>>>
>>>
>>> On 11/07/2016 18:51, David Matlack wrote:
>>>>>> vcpus have statistics associated with them which can be viewed within the
>>>>>> debugfs. Currently it is assumed within the vcpu_stat_get() and
>>>>>> vcpu_stat_get_per_vm() functions that all of these statistics are
>>>>>> represented as 32-bit numbers. The next patch adds some 64-bit statistics,
>>>>>> so add provisioning for the display of 64-bit vcpu statistics.
>>>> Thanks, we need 64-bit stats in other places as well. Can we use this
>>>> opportunity to wholesale upgrade all KVM stats from u32 to u64? Most
>>>> of this patch is duplicated code with "u32" swapped with "u64".
>>>>
>>>
>>> I'm not sure of what 32-bit architectures would do, but perhaps we could
>>> upgrade them to unsigned long at least.
>>
>> I thought u64 still existed on 32-bit architectures. unsigned long
>> would be fine but with the caveat that certain stats would overflow on
>> 32-bit architectures.
>
> Yes, but not all 32-bit architectures can do atomic read-modify-write
> (e.g. add) operations on 64-bit values.

I think that's ok, none of the stats currently use atomic operations.

>
> Paolo