Messages in this thread | | | Date | Tue, 12 May 2015 14:25:45 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched: Introduce TASK_NOLOAD and TASK_IDLE |
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On Mon, May 11, 2015 at 10:34:11PM +0300, Julian Anastasov wrote: > On Mon, 11 May 2015, Peter Zijlstra wrote: > > > > - schedule_timeout_idle (instead of schedule_timeout call): > > > __set_current_state(TASK_IDLE); > > > return schedule_timeout(timeout); > > > > > > - we here are really idle, so "N" looks ok > > > > So I don't get the point of the schedule_timeout_*() stubs. What are > > they for? Why would one use an unconditional schedule_timeout() call? > > Isn't that what msleep() is for? > > msleep will not return until timeout has expired. > Instead, we want to notice the kthread_should_stop() event > immediately. Additionally, TASK_UNINTERRUPTIBLE will increase > the load average. We can do it with extra wait queue > and the new __wait_event_idle_timeout but I guess > schedule_timeout_idle will be a good replacement for > schedule_timeout_interruptible calls when used for kthreads.
Fair enough I suppose, but then calling it schedule*() is just plain wrong, it does not behave/act like a normal schedule() call.
Lemme go look at how widely abused that is.
*sigh*, its all over the place :/
$ git grep "schedule_timeout_\(interruptible\|killable\|uninterruptible\)" | wc -l 392
That said; I still don't see the point of schedule_timeout_idle(), we should not sleep poll for state like that. We should only use TASK_IDLE when we are in fact _IDLE_ and do not have work to do, at which point one should use an wait_event() like construct to wait for new work.
> > + * like wait_event_timeout() -- except it uses TASK_IDLE to avoid loadavg > > + */ > > +#define wait_event_idle_timeout(wq, condition, timeout) \ > > +({ \ > > + long __ret = timeout; \ > > + might_sleep(); \ > > + if (!___wait_cond_timeout(condition)) \ > > + ret = __wait_event_idle_timeout(wq, condition, timeout);\ > > ret may need underscores here...
I'm fairly sure that might aid in compilation indeed :-)
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