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Subject[RFC PATCH V1 1/2] cpuidle: Data structure changes for global cpuidle device
Date
Currently cpuidle subsystem has the following data structures:

* Global cpuidle_driver which is maintained in a list for each
registered driver

* cpuidle_device is per-cpu per-driver structure that contains the
array of cpuidle_state defined for that CPU

* cpuidle_state contains the definition of the idle routine and place
holders for statistics that are used by the governor to make the
selection.

Proposed new data structures:

* Basically the cpuidle_state structure along with the cpuidle_device
is made global and per-driver. The cpuidle_state contains the idle state
definitions.

* The statistics part of the cpuidle_state that is needed by the
governor on a per-cpu bases is split into a new per-cpu structure
called cpuidle_state_stats. This structure is generic and
independent of the cpuidle_driver/device that is currently in force.


<<- Global--->> <<per-cpu>>

cpuidle_driver cpuidle_device_stats
| -> state_stats[]
\
-> cpuidle_device
-> states[]

Open Issues:

* Handle per-cpu, per-driver's driver_data appropriately within the
cpuidle_driver structure. For this RFC, it is pushed into
cpuidle_device_stats structure.

* Handle double initialization of kobj structs on multiple driver
registration.

Signed-off-by: Trinabh Gupta <trinabh@linux.vnet.ibm.com>
---
include/linux/cpuidle.h | 75 +++++++++++++++++++++++++++++++++--------------
1 files changed, 52 insertions(+), 23 deletions(-)
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index a5f5fd0..16423df 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -22,6 +22,7 @@
#define CPUIDLE_DESC_LEN 32

struct cpuidle_device;
+struct cpuidle_state_stats;


/****************************
@@ -31,18 +32,21 @@ struct cpuidle_device;
struct cpuidle_state {
char name[CPUIDLE_NAME_LEN];
char desc[CPUIDLE_DESC_LEN];
- void *driver_data;

unsigned int flags;
unsigned int exit_latency; /* in US */
unsigned int power_usage; /* in mW */
unsigned int target_residency; /* in US */

- unsigned long long usage;
- unsigned long long time; /* in US */
-
int (*enter) (struct cpuidle_device *dev,
- struct cpuidle_state *state);
+ struct cpuidle_state *state,
+ struct cpuidle_state_stats *state_stats);
+};
+
+struct cpuidle_state_stats {
+ void *driver_data;
+ unsigned long long usage;
+ unsigned long long time; /* in US */
};

/* Idle State Flags */
@@ -55,9 +59,9 @@ struct cpuidle_state {
* cpuidle_get_statedata - retrieves private driver state data
* @state: the state
*/
-static inline void * cpuidle_get_statedata(struct cpuidle_state *state)
+static inline void *cpuidle_get_statedata(struct cpuidle_state_stats *stats)
{
- return state->driver_data;
+ return stats->driver_data;
}

/**
@@ -66,9 +70,9 @@ static inline void * cpuidle_get_statedata(struct cpuidle_state *state)
* @data: the private data
*/
static inline void
-cpuidle_set_statedata(struct cpuidle_state *state, void *data)
+cpuidle_set_statedata(struct cpuidle_state_stats *state_stats, void *data)
{
- state->driver_data = data;
+ state_stats->driver_data = data;
}

struct cpuidle_state_kobj {
@@ -77,29 +81,42 @@ struct cpuidle_state_kobj {
struct kobject kobj;
};

+struct cpuidle_device_stats {
+ unsigned int enabled:1;
+ unsigned int cpu;
+ int last_residency;
+ struct cpuidle_state *last_state;
+ struct cpuidle_state_stats state_stats[CPUIDLE_STATE_MAX];
+
+ struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
+ struct kobject kobj;
+ struct completion kobj_unregister;
+
+ struct cpuidle_driver *drv;
+};
+
struct cpuidle_device {
unsigned int registered:1;
unsigned int enabled:1;
unsigned int power_specified:1;
- unsigned int cpu;

- int last_residency;
int state_count;
struct cpuidle_state states[CPUIDLE_STATE_MAX];
- struct cpuidle_state_kobj *kobjs[CPUIDLE_STATE_MAX];
- struct cpuidle_state *last_state;

- struct list_head device_list;
struct cpuidle_driver *drv;
- struct kobject kobj;
- struct completion kobj_unregister;
void *governor_data;
struct cpuidle_state *safe_state;

- int (*prepare) (struct cpuidle_device *dev);
+ int (*prepare) (struct cpuidle_device_stats *dev_stats);
};

-DECLARE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
+
+DECLARE_PER_CPU(struct cpuidle_device_stats, cpuidle_dev_stats);
+static inline struct cpuidle_state_stats *get_cpuidle_state_stats(int cpu,
+ int count)
+{
+ return &per_cpu(cpuidle_dev_stats, cpu).state_stats[count];
+}

/**
* cpuidle_get_last_residency - retrieves the last state's residency time
@@ -107,7 +124,7 @@ DECLARE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
*
* NOTE: this value is invalid if CPUIDLE_FLAG_TIME_VALID isn't set
*/
-static inline int cpuidle_get_last_residency(struct cpuidle_device *dev)
+static inline int cpuidle_get_last_residency(struct cpuidle_device_stats *dev)
{
return dev->last_residency;
}
@@ -122,6 +139,7 @@ struct cpuidle_driver {
struct module *owner;
unsigned int priority;
struct list_head driver_list;
+ struct cpuidle_device *dev;
};

#ifdef CONFIG_CPU_IDLE
@@ -145,12 +163,22 @@ static inline struct cpuidle_driver *cpuidle_get_driver(void) {return NULL; }
static inline void cpuidle_unregister_driver(struct cpuidle_driver *drv) { }
static inline int cpuidle_register_device(struct cpuidle_device *dev)
{return -ENODEV; }
+static inline int cpuidle_register_device_stats(
+ struct cpuidle_device_stats *dev_stats)
+{return -ENODEV; }
+static inline void cpuidle_unregister_device_stats(
+ struct cpuidle_device_stats *dev_stats) { };
static inline void cpuidle_unregister_device(struct cpuidle_device *dev) { }

static inline void cpuidle_pause_and_lock(void) { }
static inline void cpuidle_resume_and_unlock(void) { }
static inline int cpuidle_enable_device(struct cpuidle_device *dev)
{return -ENODEV; }
+static inline int cpuidle_enable_device_stats(
+ struct cpuidle_device_stats *dev_stats)
+{return -ENODEV; }
+static inline void cpuidle_disable_device_stats(
+ struct cpuidle_device_stats *dev_stats) { }
static inline void cpuidle_disable_device(struct cpuidle_device *dev) { }

#endif
@@ -164,11 +192,12 @@ struct cpuidle_governor {
struct list_head governor_list;
unsigned int rating;

- int (*enable) (struct cpuidle_device *dev);
- void (*disable) (struct cpuidle_device *dev);
+ int (*enable) (struct cpuidle_device_stats *dev_stats);
+ void (*disable) (struct cpuidle_device_stats *dev_stats);

- int (*select) (struct cpuidle_device *dev);
- void (*reflect) (struct cpuidle_device *dev);
+ int (*select) (struct cpuidle_device *dev,
+ struct cpuidle_device_stats *dev_stats);
+ void (*reflect) (struct cpuidle_device_stats *dev_stats);

struct module *owner;
};


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