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