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Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling feature

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On Wed, Oct 26, 2016 at 12:49:36PM +0200, Thomas Gleixner wrote:

> > +	/*
> > +	 * ITMT capability automatically enables ITMT
> > +	 * scheduling for small systems (single node).
> > +	 */
> > +	if (topology_num_packages() == 1)
> > +		sysctl_sched_itmt_enabled = 1;
> 
> I really hate this. This is policy and the kernel should not impose
> policy. Why would I like to have this enforced on my single socket XEON
> server?

So this really wants to be enabled by default; otherwise nobody will use
this, and it really does help single threaded workloads.

There were reservations on the multi-socket case of ITMT, maybe it would
help to spell those out in great detail here. That is, have the comment
explain the policy instead of simply stating what the code does (which
is always bad comment policy, you can read the code just fine).

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[PATCH v6 0/9] Support Intel® Turbo Boost Max Technology 3.0 Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 8/9] acpi: bus: Set _OSC for diverse core support Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 2/9] x86/topology: Provide topology_num_packages() Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 4/9] x86: Enable Intel Turbo Boost Max Technology 3.0 Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 3/9] x86/topology: Define x86's arch_update_cpu_topology Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling feature Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
    Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 13:00 +0200
      Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-26 20:10 +0200
        Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 20:20 +0200
          Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-26 21:40 +0200
    Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 13:00 +0200
      Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 13:30 +0200
        Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-26 19:30 +0200
          Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 20:20 +0200
      Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling feature Peter Zijlstra <peterz@infradead.org> - 2016-10-26 13:30 +0200
      Re: [PATCH v6 5/9] x86/sysctl: Add sysctl for ITMT scheduling  feature Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-26 20:10 +0200
  [PATCH v6 1/9] sched: Extend scheduler's asym packing Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
    Re: [PATCH v6 1/9] sched: Extend scheduler's asym packing Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 12:40 +0200
      Re: [PATCH v6 1/9] sched: Extend scheduler's asym packing Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-26 20:20 +0200
        Re: [PATCH v6 1/9] sched: Extend scheduler's asym packing Thomas Gleixner <tglx@linutronix.de> - 2016-10-26 20:30 +0200
  [PATCH v6 7/9] acpi: bus: Enable HWP CPPC objects Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 9/9] cpufreq: intel_pstate: Use CPPC to get max performance Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200
  [PATCH v6 6/9] x86/sched: Add SD_ASYM_PACKING flags to x86 ITMT CPU Tim Chen <tim.c.chen@linux.intel.com> - 2016-10-21 00:10 +0200

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