Re: [PATCH 3/4] sched: introduce synchronized idle injection

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From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/4] sched: introduce synchronized idle injection
Date	Fri, 27 Nov 2015 10:20:02 +0100
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* Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:

> On Wed, 18 Nov 2015 09:36:22 +0100
> Ingo Molnar <mingo@kernel.org> wrote:
> 
> > > 
> > > This patch introduces a scheduler based idle injection method, it
> > > works by blocking CFS runqueue synchronously and periodically. The
> > > actions on all online CPUs are orchestrated by per CPU hrtimers.
> > > 
> > > Two sysctl knobs are given to the userspace for selecting the
> > > percentage of idle time as well as the forced idle duration for each
> > > idle period injected.  
> > 
> > What's the purpose of these knobs? Just testing, or will some
> > user-space daemon set them dynamically?
> > 
> yes, it is to be used by userspace daemon such as thermal daemon.
> Though there are interests from in kernel thermal governor but that is
> another story.

Yeah, so let me make this very clear: for a kernel scheduling feature to be 
self-sufficient is not 'another story', but a must-have aspect for this feature
to become upstream acceptable.

We don't add scheduler features that rely on pushing 'policy' to user-space. 
That's poor design with many disadvantages. This feature should offer a reasonable 
and automatic in-kernel default behavior with numbers that prove that it works.

Keeping an essential part of the feature in user-space earns a NAK from me.

Thanks,

	Ingo
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Thread

Re: [PATCH 3/4] sched: introduce synchronized idle injection Ingo Molnar <mingo@kernel.org> - 2015-11-18 09:40 +0100
  Re: [PATCH 3/4] sched: introduce synchronized idle injection Peter Zijlstra <peterz@infradead.org> - 2015-11-18 11:40 +0100
    Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 13:30 +0100
      Re: [PATCH 3/4] sched: introduce synchronized idle injection Peter Zijlstra <peterz@infradead.org> - 2015-11-18 14:00 +0100
        Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 15:10 +0100
          Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 16:00 +0100
            Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 16:10 +0100
              Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 16:20 +0100
                Re: [PATCH 3/4] sched: introduce synchronized idle injection Thomas Gleixner <tglx@linutronix.de> - 2015-11-18 16:30 +0100
                Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 20:00 +0100
                Re: [PATCH 3/4] sched: introduce synchronized idle injection Morten Rasmussen <morten.rasmussen@arm.com> - 2015-11-18 17:10 +0100
    Re: [PATCH 3/4] sched: introduce synchronized idle injection Ingo Molnar <mingo@kernel.org> - 2015-11-27 10:20 +0100
  Re: [PATCH 3/4] sched: introduce synchronized idle injection Jacob Pan <jacob.jun.pan@linux.intel.com> - 2015-11-18 15:20 +0100
    Re: [PATCH 3/4] sched: introduce synchronized idle injection Ingo Molnar <mingo@kernel.org> - 2015-11-27 10:20 +0100
  Re: [PATCH 3/4] sched: introduce synchronized idle injection Arjan van de Ven <arjan@linux.intel.com> - 2015-11-18 15:30 +0100

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