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Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods
Date 2017-07-12 20:00 +0200
Message-ID <u2u5A-2Sc-13@gated-at.bofh.it> (permalink)
References (5 earlier) <u26mC-4Hp-23@gated-at.bofh.it> <u27LI-5Eg-25@gated-at.bofh.it> <u2oWe-8bN-11@gated-at.bofh.it> <u2sds-1H6-27@gated-at.bofh.it> <u2tsR-2Fq-11@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, Jul 12, 2017 at 07:17:56PM +0200, Peter Zijlstra wrote:
> Could be I'm just not remembering how all that works.. But I was
> wondering if we can do the expensive bits if we've decided to actually
> go NOHZ and avoid doing it on every idle entry.
> 
> IIRC the RCU fast NOHZ bits try and flush the callback list (or paw it
> off to another CPU?) such that we can go NOHZ sooner. Having a !empty
> callback list avoid NOHZ from happening.
> 
> Now if we've already decided we can't in fact go NOHZ due to other
> concerns, flushing the callback list is pointless work. So I'm thinking
> we can find a better place to do this.

I'm a wee bit confused by the split between rcu_prepare_for_idle() and
rcu_needs_cpu().

There's a fair amount overlap there.. that said, I'm thinking we should
be calling rcu_needs_cpu() as the very last test, not the very first,
such that we can bail out of tick_nohz_stop_sched_tick() without having
to incur the penalty of flushing callbacks.

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[RFC PATCH v1 00/11] Create fast idle path for short idle periods Aubrey Li <aubrey.li@intel.com> - 2017-07-10 03:50 +0200
  [RFC PATCH v1 04/11] sched/idle: make the fast idle path for short idle periods Aubrey Li <aubrey.li@intel.com> - 2017-07-10 03:50 +0200
    Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-11 15:00 +0200
      Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods Frederic Weisbecker <fweisbec@gmail.com> - 2017-07-11 18:40 +0200
        Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-11 20:20 +0200
          Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-12 05:30 +0200
            Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 07:10 +0200
              Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-12 07:30 +0200
        Re: [RFC PATCH v1 04/11] sched/idle: make the fast idle path for  short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 14:30 +0200
  [RFC PATCH v1 05/11] cpuidle: update idle statistics before cpuidle governor Aubrey Li <aubrey.li@intel.com> - 2017-07-10 03:50 +0200
  [RFC PATCH v1 08/11] cpuidle: menu: remove reduplicative implementation Aubrey Li <aubrey.li@intel.com> - 2017-07-10 04:00 +0200
  [RFC PATCH v1 07/11] cpuidle: make idle residency update more generic Aubrey Li <aubrey.li@intel.com> - 2017-07-10 04:00 +0200
  [RFC PATCH v1 03/11] cpuidle: introduce cpuidle governor for idle prediction Aubrey Li <aubrey.li@intel.com> - 2017-07-10 04:00 +0200
    Re: [RFC PATCH v1 03/11] cpuidle: introduce cpuidle governor for  idle prediction Peter Zijlstra <peterz@infradead.org> - 2017-07-12 14:20 +0200
  [RFC PATCH v1 09/11] cpuidle: menu: feed cpuidle prediction to menu governor Aubrey Li <aubrey.li@intel.com> - 2017-07-10 04:00 +0200
  Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-10 10:50 +0200
    Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Wanpeng Li <kernellwp@gmail.com> - 2017-07-10 11:40 +0200
    Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-10 16:00 +0200
    Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-10 16:50 +0200
      Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-10 18:50 +0200
        Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-10 19:30 +0200
          Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-11 06:50 +0200
            Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-11 11:50 +0200
              Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Frederic Weisbecker <fweisbec@gmail.com> - 2017-07-11 18:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-11 18:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-11 20:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 14:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 18:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 19:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 21:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 21:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 14:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 18:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 19:20 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 20:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 21:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-12 20:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-13 10:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-12 06:20 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 10:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-12 23:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-13 10:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-13 16:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-13 17:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-13 17:20 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-13 20:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-14 06:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-14 17:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-14 18:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-14 18:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-17 11:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-17 15:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-14 18:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-14 18:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-14 18:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-17 21:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-17 21:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Thomas Gleixner <tglx@linutronix.de> - 2017-07-17 21:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-17 22:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Thomas Gleixner <tglx@linutronix.de> - 2017-07-17 22:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-17 21:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Thomas Gleixner <tglx@linutronix.de> - 2017-07-17 22:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-17 22:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-18 05:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-18 05:20 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-18 06:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Thomas Gleixner <tglx@linutronix.de> - 2017-07-18 08:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Andi Kleen <ak@linux.intel.com> - 2017-07-18 09:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Thomas Gleixner <tglx@linutronix.de> - 2017-07-18 09:20 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Thomas Gleixner <tglx@linutronix.de> - 2017-07-18 09:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-18 09:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Arjan van de Ven <arjan@linux.intel.com> - 2017-07-14 18:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-13 17:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-14 05:50 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-14 06:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-17 15:30 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-17 16:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-17 16:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 14:20 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle  periods Christoph Lameter <cl@linux.com> - 2017-07-11 20:00 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-12 04:10 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods "Li, Aubrey" <aubrey.li@linux.intel.com> - 2017-07-12 04:40 +0200
                Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-12 20:20 +0200
          Re: [RFC PATCH v1 00/11] Create fast idle path for short idle periods Peter Zijlstra <peterz@infradead.org> - 2017-07-11 11:10 +0200

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