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
16 struct 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 */
37 struct prop_descriptor {
38 int index;
39 struct prop_global pg[2];
40 struct mutex mutex; /* serialize the prop_global switch */
41 };
42
43 int prop_descriptor_init(struct prop_descriptor *pd, int shift);
44 void prop_change_shift(struct prop_descriptor *pd, int new_shift);
45
46 /*
47 * ----- PERCPU ------
48 */
49
50 struct 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
64 int prop_local_init_percpu(struct prop_local_percpu *pl);
65 void prop_local_destroy_percpu(struct prop_local_percpu *pl);
66 void __prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl);
67 void prop_fraction_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl,
68 long *numerator, long *denominator);
69
70 static inline
prop_inc_percpu(struct prop_descriptor * pd,struct prop_local_percpu * pl)71 void 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
93 void __prop_inc_percpu_max(struct prop_descriptor *pd,
94 struct prop_local_percpu *pl, long frac);
95
96
97 /*
98 * ----- SINGLE ------
99 */
100
101 struct 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
120 int prop_local_init_single(struct prop_local_single *pl);
121 void prop_local_destroy_single(struct prop_local_single *pl);
122 void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
123 void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
124 long *numerator, long *denominator);
125
126 static inline
prop_inc_single(struct prop_descriptor * pd,struct prop_local_single * pl)127 void 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 */
137