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Date: Wed, 05 Jun 2013 14:37:15 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: linaro-kernel@...ts.linaro.org, patches@...aro.org,
cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org, robin.randhawa@....com,
Steve.Bannister@....com, Liviu.Dudau@....com,
charles.garcia-tobin@....com, arvind.chauhan@....com,
chenxg.marvell@...il.com
Subject: Re: [PATCH] cpufreq: userspace: Simplify governor
On Wednesday, June 05, 2013 02:34:33 PM Viresh Kumar wrote:
> Userspace governor has got more code than what it needs for its functioning.
> Lets simplify it.
OK
Why exactly is the code you're removing unnecessary?
> Over that it will fix issues in cpufreq_governor_userspace(), which isn't doing
> right things in START/STOP.
What exactly is the problem?
> It is working per-cpu currently whereas it just
> required to manage policy->cpu.
>
> Reported-by: Xiaoguang Chen <chenxg.marvell@...il.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> @Rafael:
>
> I don't know why this code was initially added. Please let me know if I am doing
> something stupid.
>
> Also, please apply it as a fix for 3.10 as it is broken recently in 3.9.
I'd love to, but I need answers to the above questions before I do that.
Thanks,
Rafael
> drivers/cpufreq/cpufreq_userspace.c | 108 ++++--------------------------------
> 1 file changed, 12 insertions(+), 96 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
> index bbeb9c0..5dc77b7 100644
> --- a/drivers/cpufreq/cpufreq_userspace.c
> +++ b/drivers/cpufreq/cpufreq_userspace.c
> @@ -13,55 +13,13 @@
>
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> -#include <linux/kernel.h>
> -#include <linux/module.h>
> -#include <linux/smp.h>
> -#include <linux/init.h>
> -#include <linux/spinlock.h>
> -#include <linux/interrupt.h>
> #include <linux/cpufreq.h>
> -#include <linux/cpu.h>
> -#include <linux/types.h>
> -#include <linux/fs.h>
> -#include <linux/sysfs.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> #include <linux/mutex.h>
>
> -/**
> - * A few values needed by the userspace governor
> - */
> -static DEFINE_PER_CPU(unsigned int, cpu_max_freq);
> -static DEFINE_PER_CPU(unsigned int, cpu_min_freq);
> -static DEFINE_PER_CPU(unsigned int, cpu_cur_freq); /* current CPU freq */
> -static DEFINE_PER_CPU(unsigned int, cpu_set_freq); /* CPU freq desired by
> - userspace */
> static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
> -
> static DEFINE_MUTEX(userspace_mutex);
> -static int cpus_using_userspace_governor;
> -
> -/* keep track of frequency transitions */
> -static int
> -userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
> - void *data)
> -{
> - struct cpufreq_freqs *freq = data;
> -
> - if (!per_cpu(cpu_is_managed, freq->cpu))
> - return 0;
> -
> - if (val == CPUFREQ_POSTCHANGE) {
> - pr_debug("saving cpu_cur_freq of cpu %u to be %u kHz\n",
> - freq->cpu, freq->new);
> - per_cpu(cpu_cur_freq, freq->cpu) = freq->new;
> - }
> -
> - return 0;
> -}
> -
> -static struct notifier_block userspace_cpufreq_notifier_block = {
> - .notifier_call = userspace_cpufreq_notifier
> -};
> -
>
> /**
> * cpufreq_set - set the CPU frequency
> @@ -80,13 +38,6 @@ static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
> if (!per_cpu(cpu_is_managed, policy->cpu))
> goto err;
>
> - per_cpu(cpu_set_freq, policy->cpu) = freq;
> -
> - if (freq < per_cpu(cpu_min_freq, policy->cpu))
> - freq = per_cpu(cpu_min_freq, policy->cpu);
> - if (freq > per_cpu(cpu_max_freq, policy->cpu))
> - freq = per_cpu(cpu_max_freq, policy->cpu);
> -
> /*
> * We're safe from concurrent calls to ->target() here
> * as we hold the userspace_mutex lock. If we were calling
> @@ -107,7 +58,7 @@ static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
>
> static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
> {
> - return sprintf(buf, "%u\n", per_cpu(cpu_cur_freq, policy->cpu));
> + return sprintf(buf, "%u\n", policy->cur);
> }
>
> static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
> @@ -119,66 +70,31 @@ static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
> switch (event) {
> case CPUFREQ_GOV_START:
> BUG_ON(!policy->cur);
> - mutex_lock(&userspace_mutex);
> -
> - if (cpus_using_userspace_governor == 0) {
> - cpufreq_register_notifier(
> - &userspace_cpufreq_notifier_block,
> - CPUFREQ_TRANSITION_NOTIFIER);
> - }
> - cpus_using_userspace_governor++;
> + pr_debug("started managing cpu %u\n", cpu);
>
> + mutex_lock(&userspace_mutex);
> per_cpu(cpu_is_managed, cpu) = 1;
> - per_cpu(cpu_min_freq, cpu) = policy->min;
> - per_cpu(cpu_max_freq, cpu) = policy->max;
> - per_cpu(cpu_cur_freq, cpu) = policy->cur;
> - per_cpu(cpu_set_freq, cpu) = policy->cur;
> - pr_debug("managing cpu %u started "
> - "(%u - %u kHz, currently %u kHz)\n",
> - cpu,
> - per_cpu(cpu_min_freq, cpu),
> - per_cpu(cpu_max_freq, cpu),
> - per_cpu(cpu_cur_freq, cpu));
> -
> mutex_unlock(&userspace_mutex);
> break;
> case CPUFREQ_GOV_STOP:
> - mutex_lock(&userspace_mutex);
> - cpus_using_userspace_governor--;
> - if (cpus_using_userspace_governor == 0) {
> - cpufreq_unregister_notifier(
> - &userspace_cpufreq_notifier_block,
> - CPUFREQ_TRANSITION_NOTIFIER);
> - }
> + pr_debug("managing cpu %u stopped\n", cpu);
>
> + mutex_lock(&userspace_mutex);
> per_cpu(cpu_is_managed, cpu) = 0;
> - per_cpu(cpu_min_freq, cpu) = 0;
> - per_cpu(cpu_max_freq, cpu) = 0;
> - per_cpu(cpu_set_freq, cpu) = 0;
> - pr_debug("managing cpu %u stopped\n", cpu);
> mutex_unlock(&userspace_mutex);
> break;
> case CPUFREQ_GOV_LIMITS:
> mutex_lock(&userspace_mutex);
> - pr_debug("limit event for cpu %u: %u - %u kHz, "
> - "currently %u kHz, last set to %u kHz\n",
> + pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz\n",
> cpu, policy->min, policy->max,
> - per_cpu(cpu_cur_freq, cpu),
> - per_cpu(cpu_set_freq, cpu));
> - if (policy->max < per_cpu(cpu_set_freq, cpu)) {
> + policy->cur);
> +
> + if (policy->max < policy->cur)
> __cpufreq_driver_target(policy, policy->max,
> CPUFREQ_RELATION_H);
> - } else if (policy->min > per_cpu(cpu_set_freq, cpu)) {
> + else if (policy->min > policy->cur)
> __cpufreq_driver_target(policy, policy->min,
> CPUFREQ_RELATION_L);
> - } else {
> - __cpufreq_driver_target(policy,
> - per_cpu(cpu_set_freq, cpu),
> - CPUFREQ_RELATION_L);
> - }
> - per_cpu(cpu_min_freq, cpu) = policy->min;
> - per_cpu(cpu_max_freq, cpu) = policy->max;
> - per_cpu(cpu_cur_freq, cpu) = policy->cur;
> mutex_unlock(&userspace_mutex);
> break;
> }
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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