1/*
  2 * FLoating proportions
  3 *
  4 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
  5 *
  6 * This file contains the public data structure and API definitions.
  7 */
  8
  9#ifndef _LINUX_PROPORTIONS_H
 10#define _LINUX_PROPORTIONS_H
 11
 12#include <linux/percpu_counter.h>
 13#include <linux/spinlock.h>
 14#include <linux/mutex.h>
 15#include <linux/gfp.h>
 16
 17struct prop_global {
 18	/*
 19	 * The period over which we differentiate
 20	 *
 21	 *   period = 2^shift
 22	 */
 23	int shift;
 24	/*
 25	 * The total event counter aka 'time'.
 26	 *
 27	 * Treated as an unsigned long; the lower 'shift - 1' bits are the
 28	 * counter bits, the remaining upper bits the period counter.
 29	 */
 30	struct percpu_counter events;
 31};
 32
 33/*
 34 * global proportion descriptor
 35 *
 36 * this is needed to consistently flip prop_global structures.
 37 */
 38struct prop_descriptor {
 39	int index;
 40	struct prop_global pg[2];
 41	struct mutex mutex;		/* serialize the prop_global switch */
 42};
 43
 44int prop_descriptor_init(struct prop_descriptor *pd, int shift, gfp_t gfp);
 45void prop_change_shift(struct prop_descriptor *pd, int new_shift);
 46
 47/*
 48 * ----- PERCPU ------
 49 */
 50
 51struct prop_local_percpu {
 52	/*
 53	 * the local events counter
 54	 */
 55	struct percpu_counter events;
 56
 57	/*
 58	 * snapshot of the last seen global state
 59	 */
 60	int shift;
 61	unsigned long period;
 62	raw_spinlock_t lock;		/* protect the snapshot state */
 63};
 64
 65int prop_local_init_percpu(struct prop_local_percpu *pl, gfp_t gfp);
 66void prop_local_destroy_percpu(struct prop_local_percpu *pl);
 67void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
 68void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
 69		long *numerator, long *denominator);
 70
 71static inline
 72void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
 73{
 74	unsigned long flags;
 75
 76	local_irq_save(flags);
 77	__prop_inc_percpu(pd, pl);
 78	local_irq_restore(flags);
 79}
 80
 81/*
 82 * Limit the time part in order to ensure there are some bits left for the
 83 * cycle counter and fraction multiply.
 84 */
 85#if BITS_PER_LONG == 32
 86#define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
 87#else
 88#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
 89#endif
 90
 91#define PROP_FRAC_SHIFT		(BITS_PER_LONG - PROP_MAX_SHIFT - 1)
 92#define PROP_FRAC_BASE		(1UL << PROP_FRAC_SHIFT)
 93
 94void __prop_inc_percpu_max(struct prop_descriptor *pd,
 95			   struct prop_local_percpu *pl, long frac);
 96
 97
 98/*
 99 * ----- SINGLE ------
100 */
101
102struct prop_local_single {
103	/*
104	 * the local events counter
105	 */
106	unsigned long events;
107
108	/*
109	 * snapshot of the last seen global state
110	 * and a lock protecting this state
111	 */
112	unsigned long period;
113	int shift;
114	raw_spinlock_t lock;		/* protect the snapshot state */
115};
116
117#define INIT_PROP_LOCAL_SINGLE(name)			\
118{	.lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock),	\
119}
120
121int prop_local_init_single(struct prop_local_single *pl);
122void prop_local_destroy_single(struct prop_local_single *pl);
123void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
124void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
125		long *numerator, long *denominator);
126
127static inline
128void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
129{
130	unsigned long flags;
131
132	local_irq_save(flags);
133	__prop_inc_single(pd, pl);
134	local_irq_restore(flags);
135}
136
137#endif /* _LINUX_PROPORTIONS_H */