Messages in this thread | | | Date | Mon, 12 Mar 2007 12:28:24 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] change futex_wait() to hrtimers |
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* Andi Kleen <andi@firstfloor.org> wrote:
> > if HIGH_RES_TIMERS is disabled then that is what happens. But > > frankly, > > disabled? I would expect it (= more wakeups) when hrtimers are > enabled.
i mean the groupping of timer expiries happens automatically when high-res is disabled. When high-res is asked for then, duh, it's enabled and you get precise timeouts ;-)
> > most futex waits are without timeouts - if an application cares > > about micro-effects like that then you are much better off not using > > a per-futex timeout anywa > > That sounds like you're arguing for not using hrtimers here because > the applications shouldn't depend on precise timeouts here anyways?!?
I was talking about the "micro-effect" of grouping timer expiries.
> Anyways when you convert more kernel timeouts to hrtimers you should > probably add some kind of batching facility that can be globally > configured with a sysctl or similar. Then at least laptops (and > possibly servers) can opt for more power saving again. For the futexes > alone it probably won't matter too much agreed, but I see a trend to > more hr.
yeah, we had that in earlier versions, it's trivial - nobody used it. So i'll wait for the actual measurements and a patch (or i can do the patch too, if someone comes up with the measurements). I've added /proc/timer_stats and /proc/timer_info for exactly such reasons.
( note that we've added the facility for even more imprecise sleeps to the timer_list APIs - but for hrtimers it's a lot less clear-cut case. )
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