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Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path

From Balbir Singh <bsingharora@gmail.com>
Newsgroups linux.kernel
Subject Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path
Date 2016-01-23 10:00 +0100
Message-ID <qU2d3-b6-1@gated-at.bofh.it> (permalink)
References <qTEkp-Kj-1@gated-at.bofh.it> <qTEkq-Kj-9@gated-at.bofh.it>
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On Fri, 22 Jan 2016 12:49:02 +0530
Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> wrote:

> cpu_to_chip_id() does a DT walk through to find out the chip id by
> taking a contended device tree lock. This adds an unnecessary overhead
> in a hot path. So instead of calling cpu_to_chip_id() everytime cache
> the chip ids for all cores in the array 'core_to_chip_map' and use it
> in the hotpath.
> 
> Reported-by: Anton Blanchard <anton@samba.org>
> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

snip

Does the core_to_chip_map need to be updated/refreshed on/after/ a
cpu (core) hotplug? I presume id's don't change

Balbir

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Thread

[PATCH v6 0/5] cpufreq: powernv: Redesign the presentation of throttle notification and solve bug-fixes in the driver Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-22 08:30 +0100
  [PATCH v6 5/5] cpufreq: powernv: Add sysfs attributes to show throttle stats Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-22 08:30 +0100
    Re: [PATCH v6 5/5] cpufreq: powernv: Add sysfs attributes to show  throttle stats Balbir Singh <bsingharora@gmail.com> - 2016-01-23 09:50 +0100
      Re: [PATCH v6 5/5] cpufreq: powernv: Add sysfs attributes to show  throttle stats Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-25 07:50 +0100
    Re: [v6, 5/5] cpufreq: powernv: Add sysfs attributes to show throttle stats Michael Ellerman <mpe@ellerman.id.au> - 2016-01-25 06:50 +0100
  [PATCH v6 3/5] cpufreq: powernv/tracing: Add powernv_throttle tracepoint Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-22 08:30 +0100
  [PATCH v6 1/5] cpufreq: powernv: Hot-plug safe the kworker thread Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-22 08:30 +0100
    Re: [PATCH v6 1/5] cpufreq: powernv: Hot-plug safe the kworker thread Viresh Kumar <viresh.kumar@linaro.org> - 2016-01-25 06:50 +0100
  [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-22 08:30 +0100
    Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from  hot-path Balbir Singh <bsingharora@gmail.com> - 2016-01-23 10:00 +0100
      Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from  hot-path Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-01-25 06:40 +0100
    Re: [PATCH v6 2/5] cpufreq: powernv: Remove cpu_to_chip_id() from  hot-path Viresh Kumar <viresh.kumar@linaro.org> - 2016-01-25 07:00 +0100
  [PATCH v6 4/5] cpufreq: powernv: Replace pr_info with trace print for throttle event Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> - 2016-01-22 08:30 +0100
    Re: [PATCH v6 4/5] cpufreq: powernv: Replace pr_info with trace  print for throttle event Viresh Kumar <viresh.kumar@linaro.org> - 2016-01-25 07:00 +0100

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