Re: [PATCH] xen: add steal_clock support on x86

Boris Ostrovsky
2016-05-18T15:25:58Z

On 05/18/2016 10:53 AM, Juergen Gross wrote:
> On 18/05/16 16:46, Boris Ostrovsky wrote:
>> On 05/18/2016 08:15 AM, Juergen Gross wrote:
>>> }
>>>
>>> +void __init xen_time_setup_guest(void)
>>> +{
>>> + pv_time_ops.steal_clock = xen_steal_clock;
>>> +
>>> + static_key_slow_inc(&paravirt_steal_enabled);
>>> + /*
>>> + * We can't set paravirt_steal_rq_enabled as this would require the
>>> + * capability to read another cpu's runstate info.
>>> + */
>>> +}
>> Won't we be accounting for stolen cycles twice now --- once from
>> steal_account_process_tick()->steal_clock() and second time from
>> do_stolen_accounting()?
> Uuh, yes.
>
> I guess I should rip do_stolen_accounting() out, too?

I don't think PARAVIRT_TIME_ACCOUNTING is always selected for Xen. If
that's indeed the case then we should ifndef do_stolen_accounting(). Or
maybe check for paravirt_steal_enabled.

-boris

> It is a
> Xen-specific hack, so I guess nobody will cry. Maybe it would be a
> good idea to select CONFIG_PARAVIRT_TIME_ACCOUNTING for XEN then?
>
>
> Juergen
>