Percentile predictor

Data Structures
struct	percpred_params_struct
	Parameters for percpred predictor. More...
struct	percpred_struct
	Percentile Predictor class definition. More...
Files
file	percpred.h
	Private interface for the Percentile Predictor.
file	percpred_lib.h
	Public interface for the Percentile predictor.
Defines
#define	PERCPRED_DEF_SAMPLESIZE   3
	Default sample size.
#define	PERCPRED_DEF_DISCARDED   0
	Default number of discarded samples (0 corresponds to WCET).
Typedefs
typedef struct percpred_params_struct	percpred_params_t
	Parameters for percpred predictor.
typedef struct percpred_struct	percpred_t
	Percentile Predictor class definition.
Functions
qos_rv	percpred_register (void)
	Register the Percentile Predictor class with the framework.
qos_rv	percpred_init (void *self, void *params)
	Initialize a percpred object.
qos_rv	percpred_final (qmgr_pred_t *self)
	Virtual destructor for a percpred object.
qos_rv	percpred_add_sample (qmgr_pred_t *pred, qres_time_t new_sample)
	Virtual add_sample function for percpred object.
qres_time_t	percpred_get_exp_value (qmgr_pred_t *pred)
qos_rv	percpred_set_defaults (void)
	Configures a Percentile predictor with default parameters.
qos_rv	percpred_set_sample_size (int sample_size)
	Sets the sample size for the Percentile predictor.
qos_rv	percpred_set_discarded (int num_discarded)
	Sets the number of samples (less than sample_size) to be discarded, in order to get the desire percentile estimate.

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Function Documentation

qos_rv percpred_add_sample	(	qmgr_pred_t *	pred,
		qres_time_t	new_sample
	)

Virtual add_sample function for percpred object.

Todo:

2 versions of this function could be created, one for the initial transitory when the window is not yet full, and another to be used when the window is full. By replacing the function pointer in the virtual table, this would avoid one comparison in the function at each call.

qos_rv percpred_init	(	void *	self,
		void *	params
	)

Initialize a percpred object.

Parameters:

params

Set of parameters passed by the QMGR Library. When in kernel-space, self is a pointer to user-space.

Returns:

QOS_OK or one of the predefined error-codes.

qos_rv percpred_set_discarded

(

int

num_discarded

)

Sets the number of samples (less than sample_size) to be discarded, in order to get the desire percentile estimate.

For example, setting it to 0 implies we want to estimate the WCET. Setting it to 1, when sample_size has been set to 12, implies we want to estimate the 91.6-th percentile (11/12 = 91.6666). Setting it to 2, when sample_size has been set to 12, implies we want to estimate the 83.3-th percentile (10/12 = 83.3333).

qos_rv percpred_set_sample_size

(

int

sample_size

)

Sets the sample size for the Percentile predictor.

Parameters:

sample_size

The number of past samples on which the moving average is computed