'cf app' shows always 0.0% cpu - how is that value measured?

Question

I never saw a value greater than 0.0% cpu on my apps. Googled also for output of cf apps and never found something other than 0.0%. Is this 0.0% from VM, container or hypervisor? How is this value calculated? Is this value collected by health manager? Can I trust this value?

Cloud Foundry runs on OpenStack cluster.

       state     since                    cpu    memory         disk          de
#0     running   2015-08-28 10:36:33 AM   0.0%   280.8M of 1G   73.7M of 4G
#1     running   2015-08-28 10:36:10 AM   0.0%   289.9M of 1G   73.7M of 4G
#2     running   2015-09-01 09:00:17 PM   0.0%   277.3M of 1G   73.7M of 4G
#3     running   2015-08-31 11:04:17 PM   0.0%   250.4M of 1G   73.7M of 4G
#4     running   2015-09-02 06:03:21 PM   0.0%   51M of 1G      73.7M of 4G
#5     running   2015-08-28 10:36:12 AM   0.0%   348.4M of 1G   73.7M of 4G
#6     running   2015-08-28 10:36:12 AM   0.0%   301.4M of 1G   73.7M of 4G
#7     running   2015-08-31 10:01:45 PM   0.0%   201.2M of 1G   73.7M of 4G
#8     running   2015-09-02 06:03:26 PM   0.0%   50.8M of 1G    73.7M of 4G
#9     running   2015-09-02 06:03:25 PM   0.0%   51.2M of 1G    73.7M of 4G
#10    running   2015-08-28 10:36:07 AM   0.0%   334.1M of 1G   73.7M of 4G
#11    running   2015-09-02 06:02:54 PM   0.0%   51.3M of 1G    73.7M of 4G
#12    running   2015-09-02 06:02:55 PM   0.0%   53.6M of 1G    73.7M of 4G
#13    running   2015-08-28 10:36:08 AM   0.0%   314M of 1G     73.7M of 4G
#14    running   2015-08-28 10:36:45 AM   0.0%   345.9M of 1G   73.7M of 4G
#15    running   2015-08-28 10:36:10 AM   0.0%   412.6M of 1G   73.7M of 4G
#16    running   2015-08-28 10:36:04 AM   0.0%   286.3M of 1G   73.7M of 4G
#17    running   2015-08-28 10:36:11 AM   0.0%   294.5M of 1G   73.7M of 4G
#18    running   2015-08-28 10:36:06 AM   0.0%   304.4M of 1G   73.7M of 4G
#19    running   2015-09-02 06:02:49 PM   0.0%   51.1M of 1G    73.7M of 4G
#20    running   2015-09-01 09:03:20 PM   0.0%   173.8M of 1G   73.7M of 4G
#21    running   2015-08-28 10:36:07 AM   0.0%   292.3M of 1G   73.7M of 4G
#22    running   2015-08-28 10:36:05 AM   0.0%   289.1M of 1G   73.7M of 4G
#23    running   2015-09-01 09:02:07 PM   0.0%   213.8M of 1G   73.7M of 4G
#24    running   2015-09-02 06:03:21 PM   0.0%   51.1M of 1G    73.7M of 4G
#25    running   2015-08-28 10:36:52 AM   0.0%   337.3M of 1G   73.7M of 4G
#26    running   2015-08-28 10:36:52 AM   0.0%   337.1M of 1G   73.7M of 4G
#27    running   2015-08-31 10:47:15 AM   0.0%   302.7M of 1G   73.7M of 4G
#28    running   2015-08-28 10:36:13 AM   0.0%   316M of 1G     73.7M of 4G
#29    running   2015-08-28 10:36:16 AM   0.0%   325.1M of 1G   73.7M of 4G
#30    running   2015-08-28 10:36:17 AM   0.0%   328.5M of 1G   73.7M of 4G
#31    running   2015-09-02 06:02:55 PM   0.0%   53.4M of 1G    73.7M of 4G
#32    running   2015-08-28 10:36:52 AM   0.0%   258.7M of 1G   73.7M of 4G
#33    running   2015-08-28 10:36:48 AM   0.0%   273.7M of 1G   73.7M of 4G
#34    running   2015-08-31 10:01:37 PM   0.0%   216.8M of 1G   73.7M of 4G
#35    running   2015-08-28 10:36:21 AM   0.0%   428.4M of 1G   73.7M of 4G
#36    running   2015-09-02 08:10:51 AM   0.0%   228.2M of 1G   73.7M of 4G
#37    running   2015-08-28 10:36:14 AM   0.0%   262.6M of 1G   73.7M of 4G
#38    running   2015-08-28 10:36:56 AM   0.0%   284.8M of 1G   73.7M of 4G
#39    running   2015-09-02 10:51:07 AM   0.0%   174.3M of 1G   73.7M of 4G
#40    running   2015-09-01 09:03:20 PM   0.0%   210.1M of 1G   73.7M of 4G
#41    running   2015-08-28 10:36:21 AM   0.0%   295.3M of 1G   73.7M of 4G
#42    running   2015-08-28 10:36:22 AM   0.0%   301.7M of 1G   73.7M of 4G
#43    running   2015-08-28 10:36:59 AM   0.0%   307M of 1G     73.7M of 4G
#44    running   2015-08-28 10:36:29 AM   0.0%   293.8M of 1G   73.7M of 4G
#45    running   2015-09-02 08:10:45 AM   0.0%   178.8M of 1G   73.7M of 4G
#46    running   2015-08-28 10:36:54 AM   0.0%   313.5M of 1G   73.7M of 4G
#47    running   2015-08-31 11:04:17 PM   0.0%   274.8M of 1G   73.7M of 4G
#48    running   2015-09-02 06:02:52 PM   0.0%   50.9M of 1G    73.7M of 4G
#49    running   2015-08-28 10:36:17 AM   0.0%   335.8M of 1G   73.7M of 4G
#50    running   2015-08-28 10:36:19 AM   0.0%   310.7M of 1G   73.7M of 4G
#51    running   2015-08-28 10:36:23 AM   0.0%   310M of 1G     73.7M of 4G
#52    running   2015-09-02 06:02:48 PM   0.0%   51M of 1G      73.7M of 4G
#53    running   2015-08-28 10:37:04 AM   0.0%   269.4M of 1G   73.7M of 4G
#54    running   2015-08-28 10:37:04 AM   0.0%   299.8M of 1G   73.7M of 4G
#55    running   2015-08-28 10:37:05 AM   0.0%   361.6M of 1G   73.7M of 4G
#56    running   2015-08-28 10:36:28 AM   0.0%   321.6M of 1G   73.7M of 4G
#57    running   2015-08-28 10:36:21 AM   0.0%   309.4M of 1G   73.7M of 4G
#58    running   2015-08-28 10:36:28 AM   0.0%   330.3M of 1G   73.7M of 4G
#59    running   2015-08-28 10:36:29 AM   0.0%   338M of 1G     73.7M of 4G
#60    running   2015-08-28 10:36:32 AM   0.0%   362.5M of 1G   73.7M of 4G
#61    running   2015-08-28 10:37:05 AM   0.0%   279.8M of 1G   73.7M of 4G
#62    running   2015-08-28 10:37:01 AM   0.0%   271.7M of 1G   73.7M of 4G
#63    running   2015-08-28 10:36:23 AM   0.0%   324M of 1G     73.7M of 4G
#64    running   2015-08-28 10:36:26 AM   0.0%   341.1M of 1G   73.7M of 4G
#65    running   2015-09-02 06:02:54 PM   0.0%   51.7M of 1G    73.7M of 4G
#66    running   2015-09-02 06:02:52 PM   0.0%   50.9M of 1G    73.7M of 4G
#67    running   2015-09-01 09:03:38 PM   0.0%   247.5M of 1G   73.7M of 4G
#68    running   2015-08-28 10:36:40 AM   0.0%   324.8M of 1G   73.7M of 4G
#69    running   2015-08-31 10:34:18 PM   0.0%   257.6M of 1G   73.7M of 4G
#70    running   2015-08-28 10:36:34 AM   0.0%   281.4M of 1G   73.7M of 4G
#71    running   2015-08-28 10:36:35 AM   0.0%   340M of 1G     73.7M of 4G
#72    running   2015-09-02 06:02:52 PM   0.0%   50.7M of 1G    73.7M of 4G
#73    running   2015-08-28 10:37:12 AM   0.0%   299.8M of 1G   73.7M of 4G
#74    running   2015-09-02 06:04:09 PM   0.0%   52.3M of 1G    73.7M of 4G
#75    running   2015-09-02 06:02:38 PM   0.0%   50.9M of 1G    73.7M of 4G
#76    running   2015-09-02 06:02:26 PM   0.0%   50.9M of 1G    73.7M of 4G
#77    running   2015-09-02 06:53:44 PM   0.0%   50.9M of 1G    73.7M of 4G
#78    running   2015-08-28 10:36:38 AM   0.0%   365.7M of 1G   73.7M of 4G
#79    running   2015-08-28 10:37:15 AM   0.0%   331.1M of 1G   73.7M of 4G
#80    running   2015-08-28 10:36:45 AM   0.0%   323.8M of 1G   73.7M of 4G
#81    running   2015-08-28 10:36:38 AM   0.0%   316.3M of 1G   73.7M of 4G
#82    running   2015-09-02 06:02:55 PM   0.0%   53.5M of 1G    73.7M of 4G
#83    running   2015-08-28 10:36:33 AM   0.0%   305.5M of 1G   73.7M of 4G
#84    running   2015-08-28 10:37:17 AM   0.0%   268.2M of 1G   73.7M of 4G
#85    running   2015-08-28 10:37:18 AM   0.0%   298.7M of 1G   73.7M of 4G
#86    running   2015-08-31 11:04:17 PM   0.0%   226.8M of 1G   73.7M of 4G
#87    running   2015-09-02 06:55:09 PM   0.0%   50.7M of 1G    73.7M of 4G
#88    running   2015-08-28 10:36:42 AM   0.0%   306.8M of 1G   73.7M of 4G
#89    running   2015-08-28 10:36:43 AM   0.0%   315.4M of 1G   73.7M of 4G
#90    running   2015-08-28 10:37:18 AM   0.0%   301.5M of 1G   73.7M of 4G
#91    running   2015-08-28 10:36:44 AM   0.0%   319.6M of 1G   73.7M of 4G
#92    running   2015-08-28 10:36:36 AM   0.0%   316.8M of 1G   73.7M of 4G
#93    running   2015-09-01 10:26:51 PM   0.0%   221.7M of 1G   73.7M of 4G
#94    running   2015-08-28 10:36:39 AM   0.0%   327.1M of 1G   73.7M of 4G
#95    running   2015-09-02 06:02:18 PM   0.0%   50.9M of 1G    73.7M of 4G
#96    running   2015-09-02 06:03:20 PM   0.0%   50.8M of 1G    73.7M of 4G
#97    running   2015-09-02 06:04:09 PM   0.0%   52.1M of 1G    73.7M of 4G
#98    running   2015-08-28 10:37:17 AM   0.0%   205.5M of 1G   73.7M of 4G
#99    running   2015-08-28 10:37:18 AM   0.0%   273.6M of 1G   73.7M of 4G
#100   running   2015-08-28 10:37:19 AM   0.0%   268.5M of 1G   73.7M of 4G
#101   running   2015-09-02 06:03:25 PM   0.0%   51M of 1G      73.7M of 4G
#102   running   2015-09-02 06:02:56 PM   0.0%   50.9M of 1G    73.7M of 4G
#103   running   2015-09-02 06:02:54 PM   0.0%   51.6M of 1G    73.7M of 4G
#104   running   2015-09-02 10:50:44 AM   0.0%   228.9M of 1G   73.7M of 4G
#105   running   2015-09-02 06:04:09 PM   0.0%   52.1M of 1G    73.7M of 4G
#106   running   2015-08-31 10:45:14 AM   0.0%   292.2M of 1G   73.7M of 4G
#107   running   2015-09-01 09:01:30 PM   0.0%   215.8M of 1G   73.7M of 4G
#108   running   2015-08-28 10:37:29 AM   0.0%   328.8M of 1G   73.7M of 4G
#109   running   2015-08-28 10:36:52 AM   0.0%   315.8M of 1G   73.7M of 4G
#110   running   2015-08-28 10:36:52 AM   0.0%   291.6M of 1G   73.7M of 4G
#111   running   2015-08-28 10:36:53 AM   0.0%   309.3M of 1G   73.7M of 4G
#112   running   2015-08-28 10:37:26 AM   0.0%   337.6M of 1G   73.7M of 4G
#113   running   2015-08-28 10:36:53 AM   0.0%   401M of 1G     73.7M of 4G
#114   running   2015-09-02 06:04:09 PM   0.0%   53M of 1G      73.7M of 4G
#115   running   2015-09-01 09:01:07 PM   0.0%   231.7M of 1G   73.7M of 4G
#116   running   2015-08-28 10:36:51 AM   0.0%   360.8M of 1G   73.7M of 4G
#117   running   2015-08-28 10:36:42 AM   0.0%   348.9M of 1G   73.7M of 4G
#118   running   2015-09-01 03:33:07 PM   0.0%   236.6M of 1G   73.7M of 4G
#119   running   2015-08-28 10:36:56 AM   0.0%   373M of 1G     73.7M of 4G
#120   running   2015-08-28 10:36:48 AM   0.0%   341.9M of 1G   73.7M of 4G
#121   running   2015-08-28 10:36:56 AM   0.0%   311.8M of 1G   73.7M of 4G
#122   running   2015-08-31 10:45:57 AM   0.0%   285.6M of 1G   73.7M of 4G
#123   running   2015-08-31 10:01:37 PM   0.0%   259.2M of 1G   73.7M of 4G
#124   running   2015-08-28 10:36:48 AM   0.0%   344.7M of 1G   73.7M of 4G
#125   running   2015-08-28 10:37:26 AM   0.0%   283.9M of 1G   73.7M of 4G
#126   running   2015-09-02 06:02:14 PM   0.0%   50.9M of 1G    73.7M of 4G
#127   running   2015-08-28 10:37:25 AM   0.0%   311.4M of 1G   73.7M of 4G

Amit Kumar Gupta · Accepted Answer

I believe the flow of info is:

cf CLI <-> Cloud Controller <-> DEA <-> Warden <-> cgroup CPU Accounting

See:

The stat here is showing you the percentage of time processes in the container spent in the CPU (of the VM) in the last second. If your application were to do something more CPU intensive, you might see this number increase. For instance, I pushed a small hello-world Golang app, which also runs a tight loop in the background where it calculates the sine value of some random float, and then cf app shows 15.5% CPU usage:

package main

import (
    "fmt"
    "net/http"
    "os"
    "math"
    "math/rand"
)

func main() {
    go func() {
        for {
            println(math.Sin(rand.Float64()))
        }
    }()

    http.HandleFunc("/", hello)
    fmt.Println("listening...")
    err := http.ListenAndServe(":"+os.Getenv("PORT"), nil)
    if err != nil {
        panic(err)
    }
}

func hello(res http.ResponseWriter, req *http.Request) {
    fmt.Fprintln(res, "go, world")
}

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