Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer.

From	Viresh Kumar <viresh.kumar@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer.
Date	2015-10-23 04:30 +0200
Message-ID	<qmAhc-4CW-9@gated-at.bofh.it> (permalink)
References	<qdLOy-7Vg-11@gated-at.bofh.it> <qitnY-7Pn-11@gated-at.bofh.it> <qlO2U-10k-69@gated-at.bofh.it> <qlZ7X-tR-7@gated-at.bofh.it> <qmw3U-6NJ-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 22-10-15, 14:40, Yunhong Jiang wrote:
> A naive question is, why it's sure a tick will happen when the tickless 
> processor is in idle?

How do you get this impression? I don't think anyone has said that.

We are talking about deferrable timers, which by design are only
required if the target CPU is not-idle. If it is idle, then the timer
isn't required to be serviced until the CPU wakes up. And the CPU can
take whatever time it wants to wake up again.

> Is it because scheduler load balance is sure to send a 
> tick to the processor in future?

No. We aren't expecting the CPU to wake up any time soon. Just ignore
the deferrable timer.

-- 
viresh
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Thread

Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-10-21 01:00 +0200
  Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Viresh Kumar <viresh.kumar@linaro.org> - 2015-10-21 12:50 +0200
    Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-10-23 00:00 +0200
      Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Viresh Kumar <viresh.kumar@linaro.org> - 2015-10-23 04:30 +0200
        Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-10-24 00:30 +0200
          Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Viresh Kumar <viresh.kumar@linaro.org> - 2015-10-24 05:30 +0200
            Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-10-26 17:40 +0100
    Re: [PATCH] timer: Lazily wakup nohz CPU when adding new timer. Frederic Weisbecker <fweisbec@gmail.com> - 2015-10-27 16:20 +0100

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