I'm making a small Android application to show current total CPU usage like tab Performance in Windows Task Manager. I use "top -m 1 -n 1 -d 1" to get CPU usage, but i do not really understand the result of "top".
The result like:
User 5%, system 15%, IOW 0%, IRQ 0%
User 5 + Nice 0 + Sys 14 + Idle 73 + IOW 0 + IRQ 0 + SIRQ 0 = 92
PID CPU% S #THR VSS RSS UID Name
213 11% R 1 900K 340K app_16 top
CPU usage = ??? How can i calculated total CPU usage?
The accepted answer for this question is incorrect. The second line of the output is the number of threads/processes that are launched in that grouping. Your CPU usage is 20% in the above. 5% of that is from user apps and 15% from system apps. You have 73 idle threads, 14 system threads, and 5 user threads (according to the second line).
for instance, here is a current top snapshot for my Droid.
User 6%, System 5%, IOW 0%, IRQ 0%
User 21 + Nice 0 + Sys 16 + Idle 270 + IOW 0 + IRQ 3 + SIRQ 0 = 310
PID CPU% S #THR VSS RSS PCY UID Name
30994 4% S 19 134912K 24140K bg app_24 edu.vu.isis.ammo.spotreport
1021 3% S 57 217400K 58504K fg system system_server
20911 2% R 1 880K 400K fg shell top
1053 0% S 1 0K 0K fg root tiwlan_wq
995 0% S 2 1272K 128K fg compass /system/bin/akmd2
According to the accepted answer, I would have 310% CPU usage, when this is actually just the number of threads. I am pretty sure I am actually using only 11% of the CPU, where the top 3 processes are using 9% of that total.
The actual answer to the question is straight-forward - can be calculated from the first line of android top's output
User 5%, system 15%, IOW 0%, IRQ 0%
Total = sum of all the percentages = 5+15 = 20%
The other answer about second line is so wrong. The second line actually gives scheduler time spent in that particular state - user/sys/idle/iow in jiffies (normally 10ms) between one output of top and the next output of top - in OP's case top -d 1 - which prints usage every second - the total number of jiffies per core would be ~100 (assuming 10ms per jiffy) - which would be similar to percentage values.
User 5 + Nice 0 + Sys 14 + Idle 73 + IOW 0 + IRQ 0 + SIRQ 0 = 92
Whereas, the values would be more if the -d is higher or if there are more than one cores
User 21 + Nice 0 + Sys 16 + Idle 270 + IOW 0 + IRQ 3 + SIRQ 0 = 310
This is probably without any -d option, so top takes default delay of 3 seconds = 300 jiffies.
Refer AOSP top sourcecode to get the complete logic of how each value is calculated.
The CPU usage percentage is given as (100-idle_percentage), more or less. In your snippet, the Idle percentage is 73, which makes your CPU usage 27%.
As for the per-process CPU usage, that will be your second column of the last 2 lines.
top command is a linux command. Have a look here
Thanks Deepak
来源：https://stackoverflow.com/questions/6134190/descrip-top-command-in-android