Re: [PATCH v2 5/6] KVM-GST: adjust scheduler cpu power

Peter Zijlstra
2011-02-01T18:59:31Z

On Tue, 2011-02-01 at 14:22 -0200, Glauber Costa wrote:
>
>
> Which tick accounting? In your other e-mail , you pointed that this only
> runs in touch_steal_time, which is fine, will change.

That tick ;-), all the account_foo muck is per tick.

> But all the rest
> here, that is behind the hypervisor specific vs generic code has nothing
> to do with ticks at all.

But I don't get it, there is no generic code needed, all that's needed
is u64 steal_time_clock(int cpu), and the first part of your
kvm_account_steal_time() function is exactly that if you add the cpu
argument.

+static u64 steal_time_clock(int cpu)
+{
+ u64 steal_time;
+ struct kvm_steal_time *src;
+ int version;
+
+ preempt_disable();
+ src = &per_cpu_ptr(steal_time, cpu);
+ do {
+ version = src->version;
+ rmb();
+ steal_time = src->steal;
+ rmb();
+ } while ((src->version & 1) || (version != src->version));
+ preempt_enable();
+
+ return steal_time
+}

And you're done.. no need to for any of that steal_time_{read,write} business.