Hi guys
Today while analyzing CPU usage of one of our processes written in go, I
noticed that there were multiple threads associated with the process which
is actually serial. (Doesn't make use of goroutines)
I wanted to know if it was the expected behaviour or some issue in our
service.
So I tested the same with this snippet:
func main() {
for {
}
}
And to my surprise, even this ever running process had multiple threads
associated with it:
➜ go build everRunningProgram.go
➜ ./everRunningProgram &
[1] 13745
➜ top -b -n 1 -H -p 13745
top - 15:07:38 up 4:03, 1 user, load average: 0.63, 0.80, 0.72
Threads: 5 total, 1 running, 4 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.9 us, 1.1 sy, 0.3 ni, 93.2 id, 0.0 wa, 0.0 hi, 0.5 si,
0.0 st
KiB Mem : 16301396 total, 4780820 free, 5033472 used, 6487104 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 10270784 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13745 mani-86+ 25 5 101856 764 584 R 99.9 0.0 0:10.38
everRunningProg
13746 mani-86+ 25 5 101856 764 584 S 0.0 0.0 0:00.00
everRunningProg
13747 mani-86+ 25 5 101856 764 584 S 0.0 0.0 0:00.00
everRunningProg
13748 mani-86+ 25 5 101856 764 584 S 0.0 0.0 0:00.00
everRunningProg
13749 mani-86+ 25 5 101856 764 584 S 0.0 0.0 0:00.00
everRunningProg
I tried the same with other programming languages and they didn't seem to
exhibit this behaviour.
*Rust:*
fn main() {
loop {}
}
➜ rustc everRunningProgram.rs
➜ ./everRunningProgram &
[2] 14265
➜ top -b -n 1 -H -p 14265
top - 15:11:36 up 4:07, 1 user, load average: 1.59, 1.29, 0.95
Threads: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.9 us, 1.1 sy, 0.5 ni, 93.0 id, 0.0 wa, 0.0 hi, 0.5 si,
0.0 st
KiB Mem : 16301396 total, 4584980 free, 5132508 used, 6583908 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 10111372 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14265 mani-86+ 25 5 13156 980 868 R 99.9 0.0 0:10.22
everRunningProg
*C:*
int main() {
while(1);
}
➜ cc everRunningProgram.c
➜ ./a.out &
[3] 14413
➜ top -b -n 1 -H -p 14413
top - 15:14:34 up 4:10, 1 user, load average: 2.43, 1.81, 1.22
Threads: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.8 us, 1.1 sy, 0.8 ni, 92.7 id, 0.0 wa, 0.0 hi, 0.5 si,
0.0 st
KiB Mem : 16301396 total, 4603696 free, 5098020 used, 6599680 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 10134048 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14413 mani-86+ 25 5 4380 712 648 R 99.9 0.0 0:06.07 a.out
*Python:*
while True:
pass
➜ scripts python3 everRunningProgram.py &
[4] 14587
➜ scripts top -b -n 1 -H -p 14587
top - 15:16:35 up 4:12, 1 user, load average: 4.08, 2.62, 1.59
Threads: 1 total, 1 running, 0 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.8 us, 1.1 sy, 1.1 ni, 92.5 id, 0.0 wa, 0.0 hi, 0.5 si,
0.0 st
KiB Mem : 16301396 total, 4551664 free, 5146576 used, 6603156 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 10082516 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14587 mani-86+ 25 5 33056 8736 5472 R 99.9 0.1 0:06.63 python3
Is there any explanation for this behaviour on Go?
What's really happening behind the scenes?
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