On Tue, 27 Aug 2019, Ming Lei wrote:
> +/*
> + * Update average irq interval with the Exponential Weighted Moving
> + * Average(EWMA)
> + */
> +static void irq_update_interval(void)
> +{
> +#define IRQ_INTERVAL_EWMA_WEIGHT 128
> +#define IRQ_INTERVAL_EWMA_PREV_FACTOR 127
> +#define IRQ_INTERVAL_EWMA_CURR_FACTOR (IRQ_INTERVAL_EWMA_WEIGHT - \
> + IRQ_INTERVAL_EWMA_PREV_FACTOR)
Please do not stick defines into a function body. That's horrible.
> +
> + int cpu = raw_smp_processor_id();
> + struct irq_interval *inter = per_cpu_ptr(&avg_irq_interval, cpu);
> + u64 delta = sched_clock_cpu(cpu) - inter->last_irq_end;
Why are you doing that raw_smp_processor_id() dance? The call site has
interrupts and preemption disabled.
Also how is that supposed to work when sched_clock is jiffies based?
> + inter->avg = (inter->avg * IRQ_INTERVAL_EWMA_PREV_FACTOR +
> + delta * IRQ_INTERVAL_EWMA_CURR_FACTOR) /
> + IRQ_INTERVAL_EWMA_WEIGHT;
We definitely are not going to have a 64bit multiplication and division on
every interrupt. Asided of that this breaks 32bit builds all over the place.
Thanks,
tglx
