Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature
Date	2016-11-08 21:00 +0100
Message-ID	<sBkIO-5kY-27@gated-at.bofh.it> (permalink)
References	(2 earlier) <sBfg6-1XK-25@gated-at.bofh.it> <sBhUC-3qu-19@gated-at.bofh.it> <sBidY-3Mc-31@gated-at.bofh.it> <sBj0l-4ko-11@gated-at.bofh.it> <sBkps-5em-47@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Nov 08, 2016 at 08:29:49PM +0100, Daniel Bristot de Oliveira wrote:
> 
> 
> On 11/08/2016 07:05 PM, Peter Zijlstra wrote:
> >> > 
> >> > I know what we want to do, but there's some momentous problems that
> >> > need to be solved first.
> > Like what?
> 
> The problem is that using RT_RUNTIME_SHARE a CPU will almost always
> borrow enough runtime to make a CPU intensive rt task to run forever...
> well not forever, but until the system crash because a kworker starved
> in this CPU. Kworkers are sched fair by design and users do not always
> have a way to avoid them in an isolated CPU, for example.
> 
> The user then can disable RT_RUNTIME_SHARE, but then the user will have
> the CPU going idle for (period - runtime) at each period... throwing CPU
> time in the trash.

So why is this a problem? You really should not be running that much
FIFO tasks to begin with.

So I'm willing to take out (or at least default disable
RT_RUNTIME_SHARE). But other than this, this never really worked to
begin with. So it cannot be a regression. And we've lived this long with
the 'problem'.

And that means this is a 'feature' and that means I say no.

We really should be doing the right thing here, not make a bigger mess.

Thread

[PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <bristot@redhat.com> - 2016-11-07 09:20 +0100
  Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Tommaso Cucinotta <tommaso.cucinotta@sssup.it> - 2016-11-07 11:40 +0100
    Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <bristot@redhat.com> - 2016-11-07 15:00 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Tommaso Cucinotta <tommaso.cucinotta@sssup.it> - 2016-11-07 19:10 +0100
        Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Luca Abeni <luca.abeni@unitn.it> - 2016-11-07 19:30 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature luca abeni <lucabe72@gmail.com> - 2016-11-08 09:00 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Juri Lelli <juri.lelli@arm.com> - 2016-11-08 11:40 +0100
  Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Christoph Lameter <cl@linux.com> - 2016-11-07 18:00 +0100
    Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 19:40 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <daniel@bristot.me> - 2016-11-07 19:50 +0100
        Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 20:20 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Christoph Lameter <cl@linux.com> - 2016-11-07 20:40 +0100
        Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Christoph Lameter <cl@linux.com> - 2016-11-07 21:00 +0100
          Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 21:10 +0100
            Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <daniel@bristot.me> - 2016-11-07 21:10 +0100
              Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 21:20 +0100
                Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <daniel@bristot.me> - 2016-11-07 21:40 +0100
                Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 21:50 +0100
                [PATCH] sched/rt: Change default setup for RT THROTTLING Daniel Bristot de Oliveira <daniel@bristot.me> - 2016-11-08 10:30 +0100
                Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Christoph Lameter <cl@linux.com> - 2016-11-09 00:50 +0100
        Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 21:10 +0100
  Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Clark Williams <williams@redhat.com> - 2016-11-07 19:30 +0100
    Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-07 19:40 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <daniel@bristot.me> - 2016-11-07 19:50 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Clark Williams <williams@redhat.com> - 2016-11-07 20:00 +0100
  Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Peter Zijlstra <peterz@infradead.org> - 2016-11-08 13:30 +0100
    Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-08 15:10 +0100
      Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Peter Zijlstra <peterz@infradead.org> - 2016-11-08 18:00 +0100
        Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Steven Rostedt <rostedt@goodmis.org> - 2016-11-08 18:20 +0100
          Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Peter Zijlstra <peterz@infradead.org> - 2016-11-08 19:10 +0100
            Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <bristot@redhat.com> - 2016-11-08 20:40 +0100
              Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Peter Zijlstra <peterz@infradead.org> - 2016-11-08 21:00 +0100
                Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Daniel Bristot de Oliveira <bristot@redhat.com> - 2016-11-09 14:40 +0100
                Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Christoph Lameter <cl@linux.com> - 2016-11-11 19:50 +0100

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