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Roland McGrath <roland@redhat.com> writes:
>
> /*
> + * This is called on clock ticks and on context switches.
> + * Bank in p->sched_time the ns elapsed since the last tick or switch.
> + */
> +static void update_cpu_clock(task_t *p, runqueue_t *rq,
> + unsigned long long now)
> +{
> + unsigned long long last = max(p->timestamp, rq->timestamp_last_tick);
> + p->sched_time += now - last;
> +}
This will completely mess up the register allocation in schedule()
long long on i386 forces basically everything else out onto the stack
because it needs 4 aligned registers.
I suspect when you benchmark it it will become visibly slower.
In general it seems like a bad idea to polute the extremly critical
fast paths in schedule with support for such an obscure operation.
Is there really any real need for such a high resolution per process
timer anyways? I have my doubts about it, I would suspect most apps
are more interested in wall clock time.
I don't think this should be merged until a clear need from a useful
application is demonstrated for it.
-Andi
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