On Tue, 7 May 2013, Ian Campbell wrote:
> On Mon, 2013-05-06 at 15:51 +0100, Stefano Stabellini wrote:
> > Register the runstate_memory_area with the hypervisor.
> > Use pv_time_ops.steal_clock to account for stolen ticks.
> >
> > Signed-off-by: Stefano Stabellini <stefano.stabell...@eu.citrix.com>
> > ---
> > arch/arm/xen/enlighten.c | 23 +++++++++++++++++++++++
> > 1 files changed, 23 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> > index ee86bfa..2a5cc82 100644
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -14,7 +14,10 @@
> > #include <xen/xen-ops.h>
> > #include <asm/xen/hypervisor.h>
> > #include <asm/xen/hypercall.h>
> > +#include <asm/arch_timer.h>
> > #include <asm/system_misc.h>
> > +#include <asm/paravirt.h>
> > +#include <linux/jump_label.h>
> > #include <linux/interrupt.h>
> > #include <linux/irqreturn.h>
> > #include <linux/module.h>
> > @@ -152,6 +155,20 @@ int xen_unmap_domain_mfn_range(struct vm_area_struct
> > *vma,
> > }
> > EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range);
> >
> > +unsigned long long xen_stolen_accounting(int cpu)
> > +{
> > + struct vcpu_runstate_info state;
> > +
> > + if (cpu != get_cpu())
>
> get_cpu disables preempt, so you need a matching put_cpu.
Oops, thanks.
> But actually I think you just want smp_processor_id and you probably
> want the BUG_ON form to get unlikely etc.
>
> That said, you don't use cpu for anything else, so why not drop it
> entirely?
Ah, that's right, legacy of the past. I'll do that.
> > + BUG();
> > +
> > + xen_get_runstate_snapshot(&state);
> > +
> > + WARN_ON(state.state != RUNSTATE_running);
> > +
> > + return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
> > +}
> > +
> > static void __init xen_percpu_init(void *unused)
> > {
> > struct vcpu_register_vcpu_info info;
> > @@ -170,6 +187,8 @@ static void __init xen_percpu_init(void *unused)
> > BUG();
> > per_cpu(xen_vcpu, cpu) = vcpup;
> >
> > + xen_setup_runstate_info(cpu);
> > +
> > enable_percpu_irq(xen_events_irq, 0);
> > }
> >
> > @@ -301,6 +320,10 @@ static int __init xen_init_events(void)
> >
> > on_each_cpu(xen_percpu_init, NULL, 0);
> >
> > + pv_time_ops.steal_clock = xen_stolen_accounting;
> > + static_key_slow_inc(¶virt_steal_enabled);
> > + static_key_slow_inc(¶virt_steal_rq_enabled);
>
> We don't seem to do this on x86 -- is that a bug on x86 on Xen?
On x86 we do all the accounting in do_stolen_accounting, called from our
own interrupt handler (xen_timer_interrupt).
I don't think we would gain anything by using the common infrastructure,
we would actually loose the idle ticks accounting we do there.
Speaking of which, I don't think that pv_time_ops.steal_clock would
properly increase CPUTIME_IDLE the way we do in do_stolen_accounting.
How much of an issue is that?
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