Commit | Line | Data |
---|---|---|
b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
c5485a7e BR |
2 | #ifndef _LINUX_AVERAGE_H |
3 | #define _LINUX_AVERAGE_H | |
4 | ||
ef4d9af6 MR |
5 | #include <linux/bug.h> |
6 | #include <linux/compiler.h> | |
7 | #include <linux/log2.h> | |
8 | ||
eb1e011a JB |
9 | /* |
10 | * Exponentially weighted moving average (EWMA) | |
11 | * | |
12 | * This implements a fixed-precision EWMA algorithm, with both the | |
13 | * precision and fall-off coefficient determined at compile-time | |
14 | * and built into the generated helper funtions. | |
15 | * | |
16 | * The first argument to the macro is the name that will be used | |
17 | * for the struct and helper functions. | |
18 | * | |
19 | * The second argument, the precision, expresses how many bits are | |
20 | * used for the fractional part of the fixed-precision values. | |
21 | * | |
22 | * The third argument, the weight reciprocal, determines how the | |
23 | * new values will be weighed vs. the old state, new values will | |
24 | * get weight 1/weight_rcp and old values 1-1/weight_rcp. Note | |
25 | * that this parameter must be a power of two for efficiency. | |
26 | */ | |
c5485a7e | 27 | |
eb1e011a | 28 | #define DECLARE_EWMA(name, _precision, _weight_rcp) \ |
2377799c JB |
29 | struct ewma_##name { \ |
30 | unsigned long internal; \ | |
31 | }; \ | |
32 | static inline void ewma_##name##_init(struct ewma_##name *e) \ | |
33 | { \ | |
eb1e011a JB |
34 | BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
35 | BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ | |
36 | /* \ | |
37 | * Even if you want to feed it just 0/1 you should have \ | |
38 | * some bits for the non-fractional part... \ | |
39 | */ \ | |
40 | BUILD_BUG_ON((_precision) > 30); \ | |
41 | BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ | |
2377799c JB |
42 | e->internal = 0; \ |
43 | } \ | |
44 | static inline unsigned long \ | |
45 | ewma_##name##_read(struct ewma_##name *e) \ | |
46 | { \ | |
eb1e011a JB |
47 | BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
48 | BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ | |
49 | BUILD_BUG_ON((_precision) > 30); \ | |
50 | BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ | |
51 | return e->internal >> (_precision); \ | |
2377799c JB |
52 | } \ |
53 | static inline void ewma_##name##_add(struct ewma_##name *e, \ | |
54 | unsigned long val) \ | |
55 | { \ | |
ef4d9af6 | 56 | unsigned long internal = READ_ONCE(e->internal); \ |
eb1e011a JB |
57 | unsigned long weight_rcp = ilog2(_weight_rcp); \ |
58 | unsigned long precision = _precision; \ | |
2377799c | 59 | \ |
eb1e011a JB |
60 | BUILD_BUG_ON(!__builtin_constant_p(_precision)); \ |
61 | BUILD_BUG_ON(!__builtin_constant_p(_weight_rcp)); \ | |
62 | BUILD_BUG_ON((_precision) > 30); \ | |
63 | BUILD_BUG_ON_NOT_POWER_OF_2(_weight_rcp); \ | |
2377799c | 64 | \ |
ef4d9af6 | 65 | WRITE_ONCE(e->internal, internal ? \ |
eb1e011a JB |
66 | (((internal << weight_rcp) - internal) + \ |
67 | (val << precision)) >> weight_rcp : \ | |
ef4d9af6 | 68 | (val << precision)); \ |
2377799c JB |
69 | } |
70 | ||
c5485a7e | 71 | #endif /* _LINUX_AVERAGE_H */ |