Messages in this thread | | | Date | Thu, 18 Dec 2014 22:12:57 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse |
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On Thu, 18 Dec 2014, Jacob Pan wrote: > OK I agree, also as I mentioned earlier, Peter already has a patch for > consolidated idle loop and remove tick_nohz_idle_enter/exit call from > powerclamp driver. I have been working on a few tweaks to maintain the > functionality and efficiency with the consolidated idle loop. > We can apply the patches on top of yours.
No. This is equally wrong as I pointed out before. The 'unified' idle loop is still fake and just pretending to be idle.
If simple standard interfaces like cpu_idle() are not working from idle code anymore then this simply stinks. And that's what any fake idle thread will do.
The whole approach is wrong. Implement a sched fair throttler and you can avoid the whoile trainwreck.
> > 1. Queue a deferable periodic timer whose handler checks if idle > > needs to be injected. If so, it sets rq->need_throttle for the cpu. > > If its already in the fake idle period, it clears rq->need_throttle > > and sets need_resched. > > > The key to powerclamp driver is to achieve package level idle > states, which implies synchronized idle injection. From > power/performance standpoint, only package level idle states is worth > injection.
Then use a synchronized non deferrable timer on all cpus. It's simple enough.
Thanks,
tglx
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