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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 */