On Fri, Aug 01, 2008 at 04:50:11PM +0200, Peter Zijlstra wrote:
> On Fri, 2008-08-01 at 09:25 -0400, Josef Bacik wrote:
>
> > Index: linux-2.6/fs/jbd/transaction.c
> > ===================================================================
> > --- linux-2.6.orig/fs/jbd/transaction.c
> > +++ linux-2.6/fs/jbd/transaction.c
>
> > @@ -63,6 +65,32 @@ get_transaction(journal_t *journal, tran
> > return transaction;
> > }
> >
> > +static void precision_sleep(unsigned long time)
> > +{
> > + struct hrtimer_sleeper t;
> > +
> > + hrtimer_init_on_stack(&t.timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
> > + hrtimer_init_sleeper(&t, current);
> > + t.timer.expires = ktime_add_ns(ktime_get_real(), time);
> > +
> > + do {
> > + set_current_state(TASK_UNINTERRUPTIBLE);
> > +
> > + hrtimer_start(&t.timer, t.timer.expires, HRTIMER_MODE_ABS);
> > + if (!hrtimer_active(&t.timer))
> > + t.task = NULL;
> > +
> > + if (likely(t.task))
> > + schedule();
> > +
> > + hrtimer_cancel(&t.timer);
> > + } while (t.task);
> > +
> > + set_current_state(TASK_RUNNING);
> > +
> > + destroy_hrtimer_on_stack(&t.timer);
> > +}
> > +
> > /*
> > * Handle management.
> > *
>
> I was convinced we already had such a creature,. but I guess I was wrong
> as I can't find it ;-)
>
> Anyway, I'm thinking this function ought to live in kernel/hrtimer.c and
> possibly get renamed to something like hrtimer_sleep_ns() or some such
> (means you can also reuse the do_nanosleep helper in there).
>
> Also, have you considered the impact on platforms that do not support
> hrtimers, or don't have high resolution clock events available?
>
Not yet :), this is just a proof of concept atm, eventually if I do use hrtimers
I would just fallback to using jiffies if the arch doesn't support hrtimers as
it still gets significantly better performance than what we currently have.
Thanks,
Josef
> > Index: linux-2.6/kernel/hrtimer.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/hrtimer.c
> > +++ linux-2.6/kernel/hrtimer.c
> > @@ -1458,6 +1458,7 @@ void hrtimer_init_sleeper(struct hrtimer
> > sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
> > #endif
> > }
> > +EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
> >
> > static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
> > {
>
> That also gets rid of this export..
>
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