/*
* FLoating proportions
*
* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <[email protected]>
*
* This file contains the public data structure and API definitions.
*/

#ifndef _LINUX_PROPORTIONS_H
#define _LINUX_PROPORTIONS_H

#include <linux/percpu_counter.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>

struct prop_global {
/*
* The period over which we differentiate
*
* period = 2^shift
*/
int shift;
/*
* The total event counter aka 'time'.
*
* Treated as an unsigned long; the lower 'shift - 1' bits are the
* counter bits, the remaining upper bits the period counter.
*/
struct percpu_counter events;
};

/*
* global proportion descriptor
*
* this is needed to consitently flip prop_global structures.
*/
struct prop_descriptor {
int index;
struct prop_global pg[2];
struct mutex mutex; /* serialize the prop_global switch */
};

int prop_descriptor_init(struct prop_descriptor *pd, int shift);
void prop_change_shift(struct prop_descriptor *pd, int new_shift);

/*
* ----- PERCPU ------
*/

struct prop_local_percpu {
/*
* the local events counter
*/
struct percpu_counter events;

/*
* snapshot of the last seen global state
*/
int shift;
unsigned long period;
raw_spinlock_t lock; /* protect the snapshot state */
};

int prop_local_init_percpu(struct prop_local_percpu *pl);
void prop_local_destroy_percpu(struct prop_local_percpu *pl);
void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
long *numerator, long *denominator);

static inline
void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
{
unsigned long flags;

local_irq_save(flags);
__prop_inc_percpu(pd, pl);
local_irq_restore(flags);
}

/*
* Limit the time part in order to ensure there are some bits left for the
* cycle counter and fraction multiply.
*/
#if BITS_PER_LONG == 32
#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
#else
#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
#endif

#define PROP_FRAC_SHIFT (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
#define PROP_FRAC_BASE (1UL << PROP_FRAC_SHIFT)

void __prop_inc_percpu_max(struct prop_descriptor *pd,
struct prop_local_percpu *pl, long frac);


/*
* ----- SINGLE ------
*/

struct prop_local_single {
/*
* the local events counter
*/
unsigned long events;

/*
* snapshot of the last seen global state
* and a lock protecting this state
*/
unsigned long period;
int shift;
raw_spinlock_t lock; /* protect the snapshot state */
};

#define INIT_PROP_LOCAL_SINGLE(name) \
{ .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \
}

int prop_local_init_single(struct prop_local_single *pl);
void prop_local_destroy_single(struct prop_local_single *pl);
void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
long *numerator, long *denominator);

static inline
void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
{
unsigned long flags;

local_irq_save(flags);
__prop_inc_single(pd, pl);
local_irq_restore(flags);
}

#endif /* _LINUX_PROPORTIONS_H */