linux-kernel - Re: [PATCH v8 0/6] cpufreq: powernv: Redesign the presentation of throttle notification and solve bug-fixes in the driver

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Date:	Wed, 3 Feb 2016 14:40:29 +0100
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...abs.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	pc@...ibm.com, anton@...ba.org, ego@...ux.vnet.ibm.com,
	shreyas@...ux.vnet.ibm.com, bsingharora@...il.com,
	mpe@...erman.id.au
Subject: Re: [PATCH v8 0/6] cpufreq: powernv: Redesign the presentation of
 throttle notification and solve bug-fixes in the driver

Hi,

On Tue, Feb 2, 2016 at 8:41 PM, Shilpasri G Bhat
<shilpa.bhat@...ux.vnet.ibm.com> wrote:
> In POWER8, OCC(On-Chip-Controller) can throttle the frequency of the
> CPU when the chip crosses its thermal and power limits. Currently,
> powernv-cpufreq driver detects and reports this event as a console
> message. Some machines may not sustain the max turbo frequency in all
> conditions and can be throttled frequently. This can lead to the
> flooding of console with throttle messages. So this patchset aims to
> redesign the presentation of this event via sysfs counters and
> tracepoints. And it also fixes couple of bugs reported in the driver.
>
> - Patch [1] fixes a memory leak bug
> - Patch [2] fixes the cpu hot-plug bug in powernv_cpufreq_work_fn().
> - Patch [3] solves a bug in powernv_cpufreq_throttle_check(), which
>   calls in to cpu_to_chip_id() in hot path which reads DT every time
>   to find the chip id.
> - Patches [4] to [6] will add a perf trace point
>   "power:powernv_throttle" and sysfs throttle counter stats in
>   /sys/devices/system/cpu/cpufreq/chipN.
>
> Changes from v7:
> - Changes in patch[6] involves adding a table to represent the
>   throtle stats in frequency X reason layout. Detailed version log
>   in the patch.
>
> Changes from v6:
> - Changes wrt comments from Balbir Singh and Viresh Kumar. Details in
>   the version log of the patches.
>
> Changes from v5:
> - Fix kbuild error:
> drivers/cpufreq/powernv-cpufreq.c:428:2: error: implicit declaration of
> function 'get_online_cpus' [-Werror=implicit-function-declaration]
>
> Changes from v4:
> - Fix a hot-plug bug in powernv_cpufreq_work_fn()
> - Changes wrt Gautham's and Shreyas's comments
>
> Changes from v3:
> - Add a fix to replace cpu_to_chip_id() with simpler PIR shift to
>   obtain the chip id.
> - Break patch2 in to two patches separating the tracepoint and sysfs
>   attribute changes.
>
> Changes from v2:
> - Fixed kbuild test warning.
> drivers/cpufreq/powernv-cpufreq.c:609:2: warning: ignoring return
> value of 'kstrtoint', declared with attribute warn_unused_result
> [-Wunused-result]
> Shilpasri G Bhat (6):
>   cpufre: powernv: Free 'chips' on module exit
>   cpufreq: powernv: Hot-plug safe the kworker thread
>   cpufreq: powernv: Remove cpu_to_chip_id() from hot-path
>   cpufreq: powernv/tracing: Add powernv_throttle tracepoint
>   cpufreq: powernv: Replace pr_info with trace print for throttle event
>   cpufreq: powernv: Add sysfs attributes to show throttle stats

It looks like patches [1-5/6] are not objectionable and I can apply
them without the last one if you want me to.

Thanks,
Rafael