On Sat, Oct 19, 2013 at 05:17:20PM +0200, Frederic Weisbecker wrote:
> +u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
> +{
> + ktime_t iowait, delta = { .tv64 = 0 };
> + struct rq *rq = cpu_rq(cpu);
> + ktime_t now = ktime_get();
> + unsigned int seq;
> +
> + do {
> + seq = read_seqbegin(&rq->iowait_lock);
> + if (rq->nr_iowait)
> + delta = ktime_sub(now, rq->iowait_start);
> + iowait = ktime_add(rq->iowait_time, delta);
> + } while (read_seqretry(&rq->iowait_lock, seq));
> +
> + if (last_update_time)
> + *last_update_time = ktime_to_us(now);
> +
> + return ktime_to_us(iowait);
> +}
> +EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
> +
> +static void cpu_iowait_start(struct rq *rq)
> +{
> + write_seqlock(&rq->iowait_lock);
> + if (!rq->nr_iowait++)
> + rq->iowait_start = ktime_get();
> + write_sequnlock(&rq->iowait_lock);
> +}
> +
> +static void cpu_iowait_end(struct rq *rq)
> +{
> + ktime_t delta;
> + write_seqlock(&rq->iowait_lock);
> + if (!--rq->nr_iowait) {
> + delta = ktime_sub(ktime_get(), rq->iowait_start);
> + rq->iowait_time = ktime_add(rq->iowait_time, delta);
> + }
> + write_sequnlock(&rq->iowait_lock);
> +}
Yeah, so using ktime_get() for this is completely insane ;-)
I just had a look at delayacct; wth wrote that crap; that too uses
gtod.
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