proportions.h

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/*
 * 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 */