Groups > linux.kernel > #1420903

Re: [patch 00/20] timer: Refactor the timer wheel

From	Eric Dumazet <edumazet@google.com>
Newsgroups	linux.kernel
Subject	Re: [patch 00/20] timer: Refactor the timer wheel
Date	2016-06-13 16:20 +0200
Message-ID	<rJASC-7p1-39@gated-at.bofh.it> (permalink)
References	<rJvJf-3OU-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Jun 13, 2016 at 1:40 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> The current timer wheel has some drawbacks:

...

> This series has also preparatory patches for changing the NOHZ timer handling
> from the current push to a pull model. Currently we decide at timer enqueue
> time on which cpu we queue the timer. This is exceptionally silly because
> there is no way to predict at enqueue time which cpu will be idle when the
> timer expires. Given the fact that most timers are canceled or rearmed before
> expiry this is even more silly. We trade a expensive decision and cross cpu
> access for a very doubtful benefit.
>

Also many TCP timers are armed from softirq handler interrupting idle task,
so scheduler believes current cpu is idle .

This patch series is really nice Thomas.

Thread

[patch 00/20] timer: Refactor the timer wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 11/20] hlist: Add hlist_is_last_node() helper Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
    Re: [patch 11/20] hlist: Add hlist_is_last_node() helper Paolo Bonzini <pbonzini@redhat.com> - 2016-06-13 12:30 +0200
  [patch 07/20] drivers/tty/mips_ejtag: Initialize timer as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 01/20] timer: Make pinned a timer property Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 17/20] tick/sched: Remove pointless empty function Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 05/20] driver/net/ethernet/tile: Initialize timer as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 15/20] timer: Move __run_timers() function Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 12/20] timer: Give a few structs and members proper names Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 04/20] cpufreq/powernv: Initialize timer as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
    Re: [patch 04/20] cpufreq/powernv: Initialize timer as pinned Arjan van de Ven <arjanvandeven@gmail.com> - 2016-06-13 15:20 +0200
  [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
    Re: [patch 13/20] timer: Switch to a non cascading wheel Peter Zijlstra <peterz@infradead.org> - 2016-06-13 13:50 +0200
      Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 14:40 +0200
        Re: [patch 13/20] timer: Switch to a non cascading wheel Eric Dumazet <edumazet@google.com> - 2016-06-13 14:50 +0200
          Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 16:40 +0200
        Re: [patch 13/20] timer: Switch to a non cascading wheel Ingo Molnar <mingo@kernel.org> - 2016-06-14 12:20 +0200
          Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-14 18:40 +0200
            Re: [patch 13/20] timer: Switch to a non cascading wheel Arjan van de Ven <arjanvandeven@gmail.com> - 2016-06-14 19:20 +0200
              Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-14 20:10 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Peter Zijlstra <peterz@infradead.org> - 2016-06-14 22:40 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Peter Zijlstra <peterz@infradead.org> - 2016-06-14 22:50 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Eric Dumazet <edumazet@google.com> - 2016-06-14 23:20 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-15 17:00 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Arjan van de Ven <arjanvandeven@gmail.com> - 2016-06-15 17:00 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-15 18:50 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-16 17:50 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-06-16 18:10 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Peter Zijlstra <peterz@infradead.org> - 2016-06-16 20:20 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-06-17 02:50 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-06-17 06:10 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Arjan van de Ven <arjanvandeven@gmail.com> - 2016-06-16 18:10 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-16 18:20 +0200
                Re: [patch 13/20] timer: Switch to a non cascading wheel Eric Dumazet <edumazet@google.com> - 2016-06-15 17:10 +0200
    Re: [patch 13/20] timer: Switch to a non cascading wheel Richard Cochran <richardcochran@gmail.com> - 2016-06-13 16:40 +0200
      Re: [patch 13/20] timer: Switch to a non cascading wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 16:50 +0200
  [patch 14/20] timer: Remove slack leftovers Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
  [patch 18/20] timer: Forward wheel clock whenever possible Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 10:50 +0200
    Re: [patch 18/20] timer: Forward wheel clock whenever possible Richard Cochran <richardcochran@gmail.com> - 2016-06-13 17:20 +0200
      Re: [patch 18/20] timer: Forward wheel clock whenever possible Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 17:30 +0200
  [patch 06/20] drivers/tty/metag_da: Initialize timer as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 11:00 +0200
    Re: [patch 06/20] drivers/tty/metag_da: Initialize timer as pinned Arjan van de Ven <arjanvandeven@gmail.com> - 2016-06-13 15:20 +0200
  [patch 03/20] x86/mce: Initialize timer as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 11:00 +0200
  [patch 08/20] net/ipv4/inet: Initialize timers as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 11:00 +0200
  [patch 02/20] x86/apic/uv: Initialize timer as pinned Thomas Gleixner <tglx@linutronix.de> - 2016-06-13 11:00 +0200
  Re: [patch 00/20] timer: Refactor the timer wheel Eric Dumazet <edumazet@google.com> - 2016-06-13 16:20 +0200
  Re: [patch 00/20] timer: Refactor the timer wheel "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-06-13 18:20 +0200
    Re: [patch 00/20] timer: Refactor the timer wheel "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-06-15 17:20 +0200
      Re: [patch 00/20] timer: Refactor the timer wheel Thomas Gleixner <tglx@linutronix.de> - 2016-06-15 19:10 +0200
        Re: [patch 00/20] timer: Refactor the timer wheel "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-06-15 22:30 +0200

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