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Re: Softirq priority inversion from "softirq: reduce latencies"

From Eric Dumazet <eric.dumazet@gmail.com>
Newsgroups linux.kernel
Subject Re: Softirq priority inversion from "softirq: reduce latencies"
Date 2016-02-29 16:30 +0100
Message-ID <r7xVM-4Nd-15@gated-at.bofh.it> (permalink)
References <r6RDc-70n-9@gated-at.bofh.it> <r72yB-6lb-1@gated-at.bofh.it> <r7d0Z-5MI-7@gated-at.bofh.it> <r7o66-5A0-5@gated-at.bofh.it> <r7xCs-4FN-45@gated-at.bofh.it>
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On lun., 2016-02-29 at 07:03 -0800, Peter Hurley wrote:

> Not the case. The softirq is raised from interrupt.
> 
> Before Eric's change, when an interrupt raises a new softirq
> while processing another softirq, the new softirq is immediately
> processed *after the existing softirq completes*.
> 
> After Eric's change, when an interrupt raises a new softirq
> while processing another softirq and _that softirq wakes a process_,
> the new softirq is *deferred to normal process priority*.

For the last time, this is not true.

My patch changed the probability for this to happen.

It will happen even if you revert it.

linux never claimed that softirq could steal all cpu time.

Are by any chance still running a HZ=100 kernel ?

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Thread

Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-27 19:20 +0100
  Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-27 21:20 +0100
    Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-27 21:40 +0100
      Re: Softirq priority inversion from "softirq: reduce latencies" David Miller <davem@davemloft.net> - 2016-02-28 00:10 +0100
        Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-28 00:40 +0100
          Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-28 03:10 +0100
            Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-28 03:20 +0100
              Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-28 03:20 +0100
              Re: Softirq priority inversion from "softirq: reduce latencies" David Miller <davem@davemloft.net> - 2016-02-28 05:50 +0100
  Re: Softirq priority inversion from "softirq: reduce latencies" Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-02-28 07:00 +0100
    Re: Softirq priority inversion from "softirq: reduce latencies" Francois Romieu <romieu@fr.zoreil.com> - 2016-02-28 18:10 +0100
      Re: Softirq priority inversion from "softirq: reduce latencies" Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-02-29 06:00 +0100
        Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-29 16:10 +0100
          Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-29 16:30 +0100
            Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-29 17:00 +0100
              Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-29 17:30 +0100
                Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-29 19:10 +0100
                Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-29 19:30 +0100
                Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-29 20:00 +0100
                Re: Softirq priority inversion from "softirq: reduce latencies" Thomas Gleixner <tglx@linutronix.de> - 2016-02-29 20:20 +0100
                Re: Softirq priority inversion from "softirq: reduce latencies" David Miller <davem@davemloft.net> - 2016-02-29 21:30 +0100
                Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-03-01 00:10 +0100
          Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-29 16:30 +0100
            Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-29 20:20 +0100
              Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-29 20:50 +0100
          Re: Softirq priority inversion from "softirq: reduce latencies" Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-02-29 16:50 +0100
            Re: Softirq priority inversion from "softirq: reduce latencies" Peter Hurley <peter@hurleysoftware.com> - 2016-02-29 17:00 +0100
              Re: Softirq priority inversion from "softirq: reduce latencies" Eric Dumazet <eric.dumazet@gmail.com> - 2016-02-29 17:30 +0100
          Re: Softirq priority inversion from "softirq: reduce latencies" David Miller <davem@davemloft.net> - 2016-02-29 18:20 +0100

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