Re: Subject: [PATCH] cpuidle: Add a sysfs entry to disable specific C state for debug purpose.

[Yanmin Zhang <yanmin_zhang@linux.intel.com>]

On Wed, 2012-02-29 at 04:55 +0000, Liu, ShuoX wrote:
> From: ShuoX Liu <shuox.liu@intel.com>
> 
> Some C states of new CPU might be not good. One reason is BIOS might configure
> them incorrectly. To help developers root cause it quickly, the patch adds a
> new sysfs entry, so developers could disable specific C state manually.
> 
> In addition, C state might have much impact on performance tuning, as it takes
> much time to enter/exit C states, which might delay interrupt processing. With
> the new debug option, developers could check if a deep C state could  impact
> performance and how much impact it could cause.
> 
> Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
Andrew,

Would you like to merge the patch into your testing tree? It's useful to help
developers debug some issues.

Thanks,
Yanmin

> ---
>  drivers/cpuidle/cpuidle.c        |    1 +
>  drivers/cpuidle/governors/menu.c |    5 ++++-
>  drivers/cpuidle/sysfs.c          |   34 ++++++++++++++++++++++++++++++++++
>  include/linux/cpuidle.h          |    1 +
>  4 files changed, 40 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 59f4261..7d66d3e 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -197,6 +197,7 @@ static void poll_idle_init(struct cpuidle_driver *drv)
>  	state->power_usage = -1;
>  	state->flags = 0;
>  	state->enter = poll_idle;
> +	state->disable = 0;
>  }
>  #else
>  static void poll_idle_init(struct cpuidle_driver *drv) {}
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index ad09526..5c17ca1 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -280,7 +280,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>  	 * We want to default to C1 (hlt), not to busy polling
>  	 * unless the timer is happening really really soon.
>  	 */
> -	if (data->expected_us > 5)
> +	if (data->expected_us > 5 &&
> +		drv->states[CPUIDLE_DRIVER_STATE_START].disable == 0)
>  		data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
>  
>  	/*
> @@ -290,6 +291,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>  	for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
>  		struct cpuidle_state *s = &drv->states[i];
>  
> +		if (s->disable)
> +			continue;
>  		if (s->target_residency > data->predicted_us)
>  			continue;
>  		if (s->exit_latency > latency_req)
> diff --git a/drivers/cpuidle/sysfs.c b/drivers/cpuidle/sysfs.c
> index 3fe41fe..1eae29a 100644
> --- a/drivers/cpuidle/sysfs.c
> +++ b/drivers/cpuidle/sysfs.c
> @@ -222,6 +222,9 @@ struct cpuidle_state_attr {
>  #define define_one_state_ro(_name, show) \
>  static struct cpuidle_state_attr attr_##_name = __ATTR(_name, 0444, show, NULL)
>  
> +#define define_one_state_rw(_name, show, store) \
> +static struct cpuidle_state_attr attr_##_name = __ATTR(_name, 0644, show, store)
> +
>  #define define_show_state_function(_name) \
>  static ssize_t show_state_##_name(struct cpuidle_state *state, \
>  			 struct cpuidle_state_usage *state_usage, char *buf) \
> @@ -229,6 +232,19 @@ static ssize_t show_state_##_name(struct cpuidle_state *state, \
>  	return sprintf(buf, "%u\n", state->_name);\
>  }
>  
> +#define define_store_state_function(_name) \
> +static ssize_t store_state_##_name(struct cpuidle_state *state, \
> +		const char *buf, size_t size) \
> +{ \
> +	int value; \
> +	sscanf(buf, "%d", &value); \
> +	if (value) \
> +		state->disable = 1; \
> +	else \
> +		state->disable = 0; \
> +	return size; \
> +}
> +
>  #define define_show_state_ull_function(_name) \
>  static ssize_t show_state_##_name(struct cpuidle_state *state, \
>  			struct cpuidle_state_usage *state_usage, char *buf) \
> @@ -251,6 +267,8 @@ define_show_state_ull_function(usage)
>  define_show_state_ull_function(time)
>  define_show_state_str_function(name)
>  define_show_state_str_function(desc)
> +define_show_state_function(disable)
> +define_store_state_function(disable)
>  
>  define_one_state_ro(name, show_state_name);
>  define_one_state_ro(desc, show_state_desc);
> @@ -258,6 +276,7 @@ define_one_state_ro(latency, show_state_exit_latency);
>  define_one_state_ro(power, show_state_power_usage);
>  define_one_state_ro(usage, show_state_usage);
>  define_one_state_ro(time, show_state_time);
> +define_one_state_rw(disable, show_state_disable, store_state_disable);
>  
>  static struct attribute *cpuidle_state_default_attrs[] = {
>  	&attr_name.attr,
> @@ -266,6 +285,7 @@ static struct attribute *cpuidle_state_default_attrs[] = {
>  	&attr_power.attr,
>  	&attr_usage.attr,
>  	&attr_time.attr,
> +	&attr_disable.attr,
>  	NULL
>  };
>  
> @@ -287,8 +307,22 @@ static ssize_t cpuidle_state_show(struct kobject * kobj,
>  	return ret;
>  }
>  
> +static ssize_t cpuidle_state_store(struct kobject *kobj,
> +	struct attribute *attr, const char *buf, size_t size)
> +{
> +	int ret = -EIO;
> +	struct cpuidle_state *state = kobj_to_state(kobj);
> +	struct cpuidle_state_attr *cattr = attr_to_stateattr(attr);
> +
> +	if (cattr->store)
> +		ret = cattr->store(state, buf, size);
> +
> +	return ret;
> +}
> +
>  static const struct sysfs_ops cpuidle_state_sysfs_ops = {
>  	.show = cpuidle_state_show,
> +	.store = cpuidle_state_store,
>  };
>  
>  static void cpuidle_state_sysfs_release(struct kobject *kobj)
> diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
> index 712abcc..eb150a5 100644
> --- a/include/linux/cpuidle.h
> +++ b/include/linux/cpuidle.h
> @@ -45,6 +45,7 @@ struct cpuidle_state {
>  	unsigned int	exit_latency; /* in US */
>  	unsigned int	power_usage; /* in mW */
>  	unsigned int	target_residency; /* in US */
> +	unsigned int    disable;
>  
>  	int (*enter)	(struct cpuidle_device *dev,
>  			struct cpuidle_driver *drv,