1/*
2** Zabbix
3** Copyright (C) 2001-2021 Zabbix SIA
4**
5** This program is free software; you can redistribute it and/or modify
6** it under the terms of the GNU General Public License as published by
7** the Free Software Foundation; either version 2 of the License, or
8** (at your option) any later version.
9**
10** This program is distributed in the hope that it will be useful,
11** but WITHOUT ANY WARRANTY; without even the implied warranty of
12** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13** GNU General Public License for more details.
14**
15** You should have received a copy of the GNU General Public License
16** along with this program; if not, write to the Free Software
17** Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
18**/
19
20package cpu
21
22const (
23	counterUnknown cpuCounter = iota - 1
24	counterUtil
25	counterLoad
26)
27
28const minimumSampleCount = 2
29
30type cpuCounters struct {
31	load float64
32	util float64
33}
34
35func counterByType(name string) (counter cpuCounter) {
36	switch name {
37	case "", "system":
38		return counterUtil
39	default:
40		return counterUnknown
41	}
42}
43
44func (c *cpuUnit) counterAverage(counter cpuCounter, period historyIndex, split int) (value interface{}) {
45	if c.head == c.tail {
46		return
47	}
48	var tail, head *cpuCounters
49	totalnum := c.tail - c.head
50	if totalnum < 0 {
51		totalnum += maxHistory
52	}
53	if totalnum < minimumSampleCount {
54		// need at least two samples to calculate change over period
55		return
56	}
57
58	if totalnum-1 < period {
59		period = totalnum - 1
60	}
61	tail = &c.history[c.tail.dec()]
62	head = &c.history[c.tail.sub(period+1)]
63
64	switch counter {
65	case counterUtil:
66		return getCounterUtil(tail, head, period)
67	case counterLoad:
68		return getCounterLoad(tail, head, period, split)
69	case counterUnknown:
70		return
71	}
72
73	return
74}
75
76func getCounterUtil(tail, head *cpuCounters, period historyIndex) interface{} {
77	if tail.util < head.util {
78		return nil
79	}
80
81	return (tail.util - head.util) / float64(period)
82}
83
84func getCounterLoad(tail, head *cpuCounters, period historyIndex, split int) interface{} {
85	if tail.load < head.load {
86		return nil
87	}
88
89	return (tail.load - head.load) / float64(split) / float64(period)
90}
91