Line data Source code
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 : 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
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 : #define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
85 :
86 : #define PROP_FRAC_SHIFT (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
87 : #define PROP_FRAC_BASE (1UL << PROP_FRAC_SHIFT)
88 :
89 : void __prop_inc_percpu_max(struct prop_descriptor *pd,
90 1 : struct prop_local_percpu *pl, long frac);
91 :
92 :
93 : /*
94 : * ----- SINGLE ------
95 : */
96 :
97 : struct prop_local_single {
98 : /*
99 : * the local events counter
100 : */
101 : unsigned long events;
102 :
103 : /*
104 : * snapshot of the last seen global state
105 : * and a lock protecting this state
106 : */
107 : unsigned long period;
108 : int shift;
109 : spinlock_t lock; /* protect the snapshot state */
110 : };
111 :
112 : #define INIT_PROP_LOCAL_SINGLE(name) \
113 : { .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
114 : }
115 :
116 : int prop_local_init_single(struct prop_local_single *pl);
117 : void prop_local_destroy_single(struct prop_local_single *pl);
118 : void __prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl);
119 : void prop_fraction_single(struct prop_descriptor *pd, struct prop_local_single *pl,
120 : long *numerator, long *denominator);
121 :
122 : static inline
123 : void prop_inc_single(struct prop_descriptor *pd, struct prop_local_single *pl)
124 : {
125 : unsigned long flags;
126 :
127 : local_irq_save(flags);
128 : __prop_inc_single(pd, pl);
129 : local_irq_restore(flags);
130 : }
131 :
132 : #endif /* _LINUX_PROPORTIONS_H */
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