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Fix improper total of CPU times (#2123)
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On linux, the cpu timer counters of user and nice include the respective guest and guest_nice counters. This results in improper calculation of percentages.

Please see:
https://github.com/torvalds/linux/blob/447976e/kernel/sched/cputime.c#L169
https://lists.linuxfoundation.org/pipermail/virtualization/2009-August/013459.html
giampaolo/psutil#940
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@Foxlik @sparrc
Foxlik authored and sparrc committed Dec 5, 2016
1 parent 504f4e6 commit 5a3f2e6
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Showing 3 changed files with 30 additions and 29 deletions.
1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -4,6 +4,7 @@

### Features

- [#2123](https://github.com/influxdata/telegraf/pull/2123): Fix improper calculation of CPU percentages
- [#1564](https://github.com/influxdata/telegraf/issues/1564): Use RFC3339 timestamps in log output.
- [#1997](https://github.com/influxdata/telegraf/issues/1997): Non-default HTTP timeouts for RabbitMQ plugin.
- [#2074](https://github.com/influxdata/telegraf/pull/2074): "discard" output plugin added, primarily for testing purposes.
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6 changes: 3 additions & 3 deletions plugins/inputs/system/cpu.go
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Expand Up @@ -91,10 +91,10 @@ func (s *CPUStats) Gather(acc telegraf.Accumulator) error {
continue
}
fieldsG := map[string]interface{}{
"usage_user": 100 * (cts.User - lastCts.User) / totalDelta,
"usage_user": 100 * (cts.User - lastCts.User - (cts.Guest - lastCts.Guest)) / totalDelta,
"usage_system": 100 * (cts.System - lastCts.System) / totalDelta,
"usage_idle": 100 * (cts.Idle - lastCts.Idle) / totalDelta,
"usage_nice": 100 * (cts.Nice - lastCts.Nice) / totalDelta,
"usage_nice": 100 * (cts.Nice - lastCts.Nice - (cts.GuestNice - lastCts.GuestNice)) / totalDelta,
"usage_iowait": 100 * (cts.Iowait - lastCts.Iowait) / totalDelta,
"usage_irq": 100 * (cts.Irq - lastCts.Irq) / totalDelta,
"usage_softirq": 100 * (cts.Softirq - lastCts.Softirq) / totalDelta,
Expand All @@ -112,7 +112,7 @@ func (s *CPUStats) Gather(acc telegraf.Accumulator) error {

func totalCpuTime(t cpu.TimesStat) float64 {
total := t.User + t.System + t.Nice + t.Iowait + t.Irq + t.Softirq + t.Steal +
t.Guest + t.GuestNice + t.Idle
t.Idle
return total
}

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52 changes: 26 additions & 26 deletions plugins/inputs/system/cpu_test.go
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Expand Up @@ -17,29 +17,29 @@ func TestCPUStats(t *testing.T) {

cts := cpu.TimesStat{
CPU: "cpu0",
User: 3.1,
User: 8.8,
System: 8.2,
Idle: 80.1,
Nice: 1.3,
Iowait: 0.2,
Irq: 0.1,
Iowait: 0.8389,
Irq: 0.6,
Softirq: 0.11,
Steal: 0.0511,
Guest: 8.1,
Guest: 3.1,
GuestNice: 0.324,
}

cts2 := cpu.TimesStat{
CPU: "cpu0",
User: 11.4, // increased by 8.3
User: 24.9, // increased by 16.1
System: 10.9, // increased by 2.7
Idle: 158.8699, // increased by 78.7699 (for total increase of 100)
Nice: 2.5, // increased by 1.2
Iowait: 0.7, // increased by 0.5
Irq: 1.2, // increased by 1.1
Idle: 157.9798, // increased by 77.8798 (for total increase of 100)
Nice: 3.5, // increased by 2.2
Iowait: 0.929, // increased by 0.0901
Irq: 1.2, // increased by 0.6
Softirq: 0.31, // increased by 0.2
Steal: 0.2812, // increased by 0.0001
Guest: 12.9, // increased by 4.8
Steal: 0.2812, // increased by 0.2301
Guest: 11.4, // increased by 8.3
GuestNice: 2.524, // increased by 2.2
}

Expand All @@ -56,15 +56,15 @@ func TestCPUStats(t *testing.T) {

// Computed values are checked with delta > 0 becasue of floating point arithmatic
// imprecision
assertContainsTaggedFloat(t, &acc, "cpu", "time_user", 3.1, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_user", 8.8, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_system", 8.2, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_idle", 80.1, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_nice", 1.3, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_iowait", 0.2, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_irq", 0.1, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_iowait", 0.8389, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_irq", 0.6, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_softirq", 0.11, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_steal", 0.0511, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_guest", 8.1, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_guest", 3.1, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_guest_nice", 0.324, 0, cputags)

mps2 := MockPS{}
Expand All @@ -75,26 +75,26 @@ func TestCPUStats(t *testing.T) {
err = cs.Gather(&acc)
require.NoError(t, err)

assertContainsTaggedFloat(t, &acc, "cpu", "time_user", 11.4, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_user", 24.9, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_system", 10.9, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_idle", 158.8699, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_nice", 2.5, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_iowait", 0.7, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_idle", 157.9798, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_nice", 3.5, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_iowait", 0.929, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_irq", 1.2, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_softirq", 0.31, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_steal", 0.2812, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_guest", 12.9, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_guest", 11.4, 0, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "time_guest_nice", 2.524, 0, cputags)

assertContainsTaggedFloat(t, &acc, "cpu", "usage_user", 8.3, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_user", 7.8, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_system", 2.7, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_idle", 78.7699, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_nice", 1.2, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_iowait", 0.5, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_irq", 1.1, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_idle", 77.8798, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_nice", 0, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_iowait", 0.0901, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_irq", 0.6, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_softirq", 0.2, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_steal", 0.2301, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_guest", 4.8, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_guest", 8.3, 0.0005, cputags)
assertContainsTaggedFloat(t, &acc, "cpu", "usage_guest_nice", 2.2, 0.0005, cputags)
}

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