Re: [PATCH 16/16] Thermal: use plist instead of list

From: Zhang Rui <rui.zhang@intel.com>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Amit Kachhap <amit.kachhap@linaro.org>,
	linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org,
	Matthew Garrett <mjg@redhat.com>, Len Brown <lenb@kernel.org>,
	R Durgadoss <durgadoss.r@intel.com>, Wei Ni <wni@nvidia.com>,
	eduardo <eduardo.valentin@ti.com>
Subject: Re: [PATCH 16/16] Thermal: use plist instead of list
Date: Tue, 24 Jul 2012 10:13:29 +0800	[thread overview]
Message-ID: <1343096009.1682.365.camel@rui.sh.intel.com> (raw)
In-Reply-To: <201207192345.20753.rjw@sisk.pl>

On 四, 2012-07-19 at 23:45 +0200, Rafael J. Wysocki wrote:
> On Thursday, July 19, 2012, Zhang Rui wrote:
> > so that the thermal manager can easily find out
> > the deepest cooling state request for a cooling device.
> > 
> > cdev->lock is also introduced in this patch to protect this plist.
> > 
> > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> 
> I'm not sure if this is actually better than without the plist.
> 
> The plist manipulations in thermal_zone_trip_update() look like they
> can add quite some overhead in some situations.
> 
> Do you have any quantitative justification for this change?
> 
No.
I made this change based on Eduardo's suggestion.
currently, as there are not too many nodes in the list, I don't think we
can get any measurable benefit for now.

Eduardo, I guess you must have more to say on this. :p

thanks,
rui

> Rafael
> 
> 
> > ---
> >  drivers/thermal/thermal_sys.c |   84 ++++++++++++++++++++++++++---------------
> >  include/linux/thermal.h       |    4 +-
> >  2 files changed, 57 insertions(+), 31 deletions(-)
> > 
> > diff --git a/drivers/thermal/thermal_sys.c b/drivers/thermal/thermal_sys.c
> > index a40dda1..9f56250 100644
> > --- a/drivers/thermal/thermal_sys.c
> > +++ b/drivers/thermal/thermal_sys.c
> > @@ -54,11 +54,10 @@ struct thermal_instance {
> >  	int trip;
> >  	unsigned long upper;	/* Highest cooling state for this trip point */
> >  	unsigned long lower;	/* Lowest cooling state for this trip point */
> > -	unsigned long target;	/* expected cooling state */
> >  	char attr_name[THERMAL_NAME_LENGTH];
> >  	struct device_attribute attr;
> >  	struct list_head tz_node; /* node in tz->instances */
> > -	struct list_head cdev_node; /* node in cdev->instances */
> > +	struct plist_node cdev_node; /* node in cdev->instances */
> >  };
> >  
> >  static DEFINE_IDR(thermal_tz_idr);
> > @@ -787,7 +786,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
> >  	dev->trip = trip;
> >  	dev->upper = upper;
> >  	dev->lower = lower;
> > -	dev->target = -1;
> > +	plist_node_init(&dev->cdev_node, -1);
> >  
> >  	result = get_idr(&tz->idr, &tz->lock, &dev->id);
> >  	if (result)
> > @@ -809,6 +808,7 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
> >  		goto remove_symbol_link;
> >  
> >  	mutex_lock(&tz->lock);
> > +	mutex_lock(&cdev->lock);
> >  	list_for_each_entry(pos, &tz->instances, tz_node)
> >  	    if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
> >  		result = -EEXIST;
> > @@ -816,8 +816,9 @@ int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
> >  	}
> >  	if (!result) {
> >  		list_add_tail(&dev->tz_node, &tz->instances);
> > -		list_add_tail(&dev->cdev_node, &cdev->instances);
> > +		plist_add(&dev->cdev_node, &cdev->instances);
> >  	}
> > +	mutex_unlock(&cdev->lock);
> >  	mutex_unlock(&tz->lock);
> >  
> >  	if (!result)
> > @@ -850,14 +851,17 @@ int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
> >  	struct thermal_instance *pos, *next;
> >  
> >  	mutex_lock(&tz->lock);
> > +	mutex_lock(&cdev->lock);
> >  	list_for_each_entry_safe(pos, next, &tz->instances, tz_node) {
> >  		if (pos->tz == tz && pos->trip == trip && pos->cdev == cdev) {
> >  			list_del(&pos->tz_node);
> > -			list_del(&pos->cdev_node);
> > +			plist_del(&pos->cdev_node, &pos->cdev->instances);
> > +			mutex_unlock(&cdev->lock);
> >  			mutex_unlock(&tz->lock);
> >  			goto unbind;
> >  		}
> >  	}
> > +	mutex_unlock(&cdev->lock);
> >  	mutex_unlock(&tz->lock);
> >  
> >  	return -ENODEV;
> > @@ -923,7 +927,8 @@ thermal_cooling_device_register(char *type, void *devdata,
> >  	}
> >  
> >  	strcpy(cdev->type, type);
> > -	INIT_LIST_HEAD(&cdev->instances);
> > +	plist_head_init(&cdev->instances);
> > +	mutex_init(&cdev->lock);
> >  	cdev->ops = ops;
> >  	cdev->updated = 1;
> >  	cdev->device.class = &thermal_class;
> > @@ -1019,26 +1024,21 @@ EXPORT_SYMBOL(thermal_cooling_device_unregister);
> >  
> >  static void thermal_zone_do_update(struct thermal_zone_device *tz)
> >  {
> > -	struct thermal_instance *instance1, *instance2;
> > +	struct thermal_instance *instance;
> > +	struct plist_node *node;
> >  	struct thermal_cooling_device *cdev;
> > -	int target;
> >  
> > -	list_for_each_entry(instance1, &tz->instances, tz_node) {
> > -		cdev = instance1->cdev;
> > +	list_for_each_entry(instance, &tz->instances, tz_node) {
> > +		cdev = instance->cdev;
> >  
> >  		/* cooling device has already been updated*/
> >  		if (cdev->updated)
> >  			continue;
> >  
> > -		target = 0;
> > -		/* Make sure cdev enters the deepest cooling state */
> > -		list_for_each_entry(instance2, &cdev->instances, cdev_node) {
> > -			if (instance2->target == -1)
> > -				continue;
> > -			if (instance2->target > target)
> > -				target = instance2->target;
> > -		}
> > -		cdev->ops->set_cur_state(cdev, target);
> > +		/* Deepest cooling state required */
> > +		node = plist_last(&cdev->instances);
> > +
> > +		cdev->ops->set_cur_state(cdev, node->prio < 0 ? 0 : node->prio);
> >  		cdev->updated = 1;
> >  	}
> >  }
> > @@ -1064,7 +1064,7 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
> >  {
> >  	struct thermal_instance *instance;
> >  	struct thermal_cooling_device *cdev = NULL;
> > -	unsigned long cur_state, max_state;
> > +	unsigned long cur_state, max_state, target_state;
> >  	long trip_temp;
> >  	enum thermal_trip_type trip_type;
> >  	enum thermal_trend trend;
> > @@ -1088,21 +1088,29 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
> >  
> >  			cdev->ops->get_cur_state(cdev, &cur_state);
> >  			cdev->ops->get_max_state(cdev, &max_state);
> > -
> > +			target_state = cur_state;
> >  			if (trend == THERMAL_TREND_RAISING) {
> > -				cur_state = cur_state < instance->upper ?
> > +				target_state = cur_state < instance->upper ?
> >  					    (cur_state + 1) : instance->upper;
> >  			} else if (trend == THERMAL_TREND_DROPPING) {
> > -				cur_state = cur_state > instance->lower ?
> > +				target_state = cur_state > instance->lower ?
> >  				    (cur_state - 1) : instance->lower;
> >  			}
> >  
> > +			if (target_state == cur_state)
> > +				continue;
> > +
> >  			/* activate a passive thermal instance */
> >  			if (trip_type == THERMAL_TRIP_PASSIVE &&
> > -			    instance->target == -1)
> > +			    instance->cdev_node.prio == -1)
> >  				tz->passive++;
> >  
> > -			instance->target = cur_state;
> > +			mutex_lock(&cdev->lock);
> > +			plist_del(&instance->cdev_node, &cdev->instances);
> > +			plist_node_init(&instance->cdev_node, target_state);
> > +			plist_add(&instance->cdev_node, &cdev->instances);
> > +			mutex_unlock(&cdev->lock);
> > +
> >  			cdev->updated = 0; /* cooling device needs update */
> >  		}
> >  	} else {	/* below trip */
> > @@ -1111,20 +1119,36 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz,
> >  				continue;
> >  
> >  			/* Do not use the deacitve thermal instance */
> > -			if (instance->target == -1)
> > +			if (instance->cdev_node.prio == -1)
> >  				continue;
> >  			cdev = instance->cdev;
> >  			cdev->ops->get_cur_state(cdev, &cur_state);
> >  
> > -			cur_state = cur_state > instance->lower ?
> > +			target_state = cur_state > instance->lower ?
> >  				    (cur_state - 1) : -1;
> >  
> > +			if (target_state == cur_state)
> > +				continue;
> > +
> >  			/* deactivate a passive thermal instance */
> >  			if (trip_type == THERMAL_TRIP_PASSIVE &&
> > -			    cur_state == -1)
> > +			    target_state == -1)
> >  				tz->passive--;
> > -			instance->target = cur_state;
> > -			cdev->updated = 0; /* cooling device needs update */
> > +
> > +			mutex_lock(&cdev->lock);
> > +			plist_del(&instance->cdev_node, &cdev->instances);
> > +			plist_node_init(&instance->cdev_node, target_state);
> > +			plist_add(&instance->cdev_node, &cdev->instances);
> > +			mutex_unlock(&cdev->lock);
> > +
> > +			/*
> > +			 * cooling device needs update.
> > +			 * But if the target_state is -1, it means that
> > +			 * the cooling device is already in cooling state 0,
> > +			 * thus we do not need update
> > +			 */
> > +			if (target_state != -1)
> > +				cdev->updated = 0;
> >  		}
> >  	}
> >  
> > diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> > index f725eb9..376a59e 100644
> > --- a/include/linux/thermal.h
> > +++ b/include/linux/thermal.h
> > @@ -28,6 +28,7 @@
> >  #include <linux/idr.h>
> >  #include <linux/device.h>
> >  #include <linux/workqueue.h>
> > +#include <linux/plist.h>
> >  
> >  struct thermal_zone_device;
> >  struct thermal_cooling_device;
> > @@ -93,7 +94,8 @@ struct thermal_cooling_device {
> >  	void *devdata;
> >  	const struct thermal_cooling_device_ops *ops;
> >  	int updated; /* 1 if the cooling device does not need update */
> > -	struct list_head instances;
> > +	struct mutex lock;
> > +	struct plist_head instances;
> >  	struct list_head node;
> >  };
> >  
> > 
> 

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