[linux] 量測特定 process CPU ussage

Preparation

To calculate CPU usage for a specific process you'll need the following:

1. /proc/uptime
   • #1 uptime of the system (seconds)
2. /proc/[PID]/stat
   • #14 utime - CPU time spent in user code, measured in clock ticks
   • #15 stime - CPU time spent in kernel code, measured in clock ticks
   • #16 cutime - Waited-for children's CPU time spent in user code (in clock ticks)
   • #17 cstime - Waited-for children's CPU time spent in kernel code (in clock ticks)
   • #22 starttime - Time when the process started, measured in clock ticks
3. Hertz (number of clock ticks per second) of your system.
• In most cases, getconf CLK_TCK can be used to return the number of clock ticks.
• The sysconf(_SC_CLK_TCK) C function call may also be used to return the hertz value.

Calculation

First we determine the total time spent for the process:

total_time = utime + stime

We also have to decide whether we want to include the time from children processes. If we do, then we add those values to total_time:

total_time = total_time + cutime + cstime

Next we get the total elapsed time in seconds since the process started:

seconds = uptime - (starttime / Hertz)

Finally we calculate the CPU usage percentage:

cpu_usage = 100 * ((total_time / Hertz) / seconds)
















此例來說 bash 的 CPU usage 為
1.160880760010654




ref:
http://stackoverflow.com/questions/16726779/how-do-i-get-the-total-cpu-usage-of-an-application-from-proc-pid-stat

[Android] 改設定以免 Android Studio 吃 C槽 系統硬碟空間

1.
C:\Program Files\Android Studio\bin\idea.propertis

idea.config.path
idea.system.path

2.
環境變數
Variable name: ANDROID_SDK_HOME
Variable value: D:\Android



3.





參考這篇但改變順序
以免重工
http://www.littlecpu.com/android-studio-c-drive

[C]如何在 linux 和 Mac build C share library

以此例來說，quanto2 是我們要build 的目的檔案



gcc -fPIC -g -c quanto2.c -o libquanto2.o

Linux:
gcc -g -shared -Wl,-soname,libquanto2.so -o libquanto2.so libquanto2.o -lc
MacOS:
gcc -g -shared -Wl,-install_name,libquanto2.so -o libquanto2.so libquanto2.o -lc


gcc -g test.c -o test -L. -lquanto2

[Go] 如何和 C 語言做介接

以這個為例 ，quanto2 是我的自定義 C library
這樣就可以call 到 C 的 function



// #cgo LDFLAGS: -L ./ -lquanto2
// #include <stdio.h>
// #include <stdlib.h>
// #include "quanto2.h"
import "C"
import "fmt"

func main() {
    fmt.Println("ho ho")
    C.testGo()
}