load_tracking.h revision da30fdf9
1/*
2 * Copyright 2013 Pawe�� Dziepak, pdziepak@quarnos.org.
3 * Distributed under the terms of the MIT License.
4 */
5#ifndef _KERNEL_LOAD_TRACKING_H
6#define _KERNEL_LOAD_TRACKING_H
7
8
9#include <OS.h>
10
11
12const int32 kMaxLoad = 1000;
13const bigtime_t kLoadMeasureInterval = 1000;
14const bigtime_t kIntervalInaccuracy = kLoadMeasureInterval / 4;
15
16
17static inline int32
18compute_load(bigtime_t& measureTime, bigtime_t& measureActiveTime, int32& load,
19	bigtime_t now)
20{
21	if (measureTime == 0) {
22		measureTime = now;
23		return -1;
24	}
25
26	bigtime_t deltaTime = now - measureTime;
27
28	if (deltaTime < kLoadMeasureInterval)
29		return -1;
30
31	int32 oldLoad = load;
32	ASSERT(oldLoad >= 0 && oldLoad <= kMaxLoad);
33
34	int32 newLoad = measureActiveTime * kMaxLoad;
35	newLoad /= max_c(deltaTime, 1);
36	newLoad = max_c(min_c(newLoad, kMaxLoad), 0);
37
38	measureActiveTime = 0;
39	measureTime = now;
40
41	deltaTime += kIntervalInaccuracy;
42	bigtime_t n = deltaTime / kLoadMeasureInterval;
43	ASSERT(n > 0);
44
45	if (n > 10)
46		load = newLoad;
47	else {
48		newLoad *= (1 << n) - 1;
49		load = (load + newLoad) / (1 << n);
50		ASSERT(load >= 0 && load <= kMaxLoad);
51	}
52
53	return oldLoad;
54}
55
56
57#endif	// _KERNEL_LOAD_TRACKING_H
58