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    SubjectRe: [PATCH 2/6] Add IRQ_TIME_ACCOUNTING, finer accounting of CPU irq time
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    On Thu, 2010-09-16 at 18:56 -0700, Venkatesh Pallipadi wrote:
    >
    > Signed-off-by: Venkatesh Pallipadi <venki@google.com>
    > ---
    > include/linux/hardirq.h | 2 +-
    > include/linux/sched.h | 11 +++++++++++
    > kernel/sched.c | 38 ++++++++++++++++++++++++++++++++++++++
    > 3 files changed, 50 insertions(+), 1 deletions(-)
    >
    > diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
    > index ce22d09..bfafd29 100644
    > --- a/include/linux/hardirq.h
    > +++ b/include/linux/hardirq.h
    > @@ -132,7 +132,7 @@ extern void synchronize_irq(unsigned int irq);
    >
    > struct task_struct;
    >
    > -#ifndef CONFIG_VIRT_CPU_ACCOUNTING
    > +#if !defined(CONFIG_VIRT_CPU_ACCOUNTING) && !defined(CONFIG_IRQ_TIME_ACCOUNTING)
    > static inline void account_system_vtime(struct task_struct *tsk)
    > {
    > }
    > diff --git a/include/linux/sched.h b/include/linux/sched.h
    > index 1e2a6db..dbb6808 100644
    > --- a/include/linux/sched.h
    > +++ b/include/linux/sched.h
    > @@ -1826,6 +1826,17 @@ extern void sched_clock_idle_sleep_event(void);
    > extern void sched_clock_idle_wakeup_event(u64 delta_ns);
    > #endif
    >
    > +#ifdef CONFIG_IRQ_TIME_ACCOUNTING
    > +/*
    > + * An i/f to runtime opt-in for irq time accounting based off of sched_clock.
    > + * The reason for this explicit opt-in is not to have perf penalty with
    > + * slow sched_clocks.
    > + */
    > +extern void enable_sched_clock_irqtime(void);
    > +#else
    > +static inline void enable_sched_clock_irqtime(void) {}
    > +#endif
    > +
    > extern unsigned long long
    > task_sched_runtime(struct task_struct *task);
    > extern unsigned long long thread_group_sched_runtime(struct task_struct *task);
    > diff --git a/kernel/sched.c b/kernel/sched.c
    > index ed09d4f..912d2de 100644
    > --- a/kernel/sched.c
    > +++ b/kernel/sched.c
    > @@ -1917,6 +1917,44 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
    > dec_nr_running(rq);
    > }
    >
    > +#ifdef CONFIG_IRQ_TIME_ACCOUNTING
    > +
    > +static DEFINE_PER_CPU(u64, cpu_hardirq_time);
    > +static DEFINE_PER_CPU(u64, cpu_softirq_time);
    > +
    > +static DEFINE_PER_CPU(u64, irq_start_time);
    > +static int sched_clock_irqtime;
    > +
    > +void enable_sched_clock_irqtime(void)
    > +{
    > + sched_clock_irqtime = 1;
    > +}
    > +
    > +void account_system_vtime(struct task_struct *tsk)
    > +{
    > + unsigned long flags;
    > + int cpu;
    > + u64 now, delta;
    > +
    > + if (!sched_clock_irqtime)
    > + return;
    > +
    > + local_irq_save(flags);
    > +
    > + cpu = task_cpu(tsk);

    Can this ever be anything other can smp_processor_id() and current?

    > + now = sched_clock();

    this should be using one of the kernel/sched_clock.c thingies, probably
    local_clock(), or sched_clock_cpu(cpu).

    > + delta = now - per_cpu(irq_start_time, cpu);
    > + per_cpu(irq_start_time, cpu) = now;
    > + if (hardirq_count())
    > + per_cpu(cpu_hardirq_time, cpu) += delta;
    > + else if (softirq_count())
    > + per_cpu(cpu_softirq_time, cpu) += delta;
    > +
    > + local_irq_restore(flags);
    > +}

    Also, this isn't a complete API, its very asymmetric, please cure that.


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