i/o disk
by vucni45 from LinuxQuestions.org on (#5QJ76)
Hi,
I like to understand why a cpu is loaded 100% with a process that wait for i/o disk to complete.
I know that when a process starts an interruptible i/o then this process goes in waiting queue and the cpu runs other task.
mount 192.168.1.9:/test /y is on 192.168.1.4
dd if=/dev/zero of=/y/y bs=1K count=10000000
on 192.168.1.9 systemctl stop nfs-server
on 192.168.1.4
top -p 1849
Code: top -p 1849
top - 03:39:24 up 5 min, 3 users, load average: 0.66, 0.71, 0.39
Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.0 us, 0.0 sy, 0.0 ni, 0.0 id,100.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu1 : 0.0 us, 0.3 sy, 0.0 ni, 99.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1849 root 20 0 108100 616 520 D 0.0 0.0 0:05.24 ddcpu0
0.0 id,100.0 wa ->it means that cpu0 is busy 100%?
then under %CPU is 0.0->?
i expected that cpu0 or cpu1 to run other task until i/o completes.
it seems that cpu0 givea all the cpu cycles to process 1849.
I like to understand why a cpu is loaded 100% with a process that wait for i/o disk to complete.
I know that when a process starts an interruptible i/o then this process goes in waiting queue and the cpu runs other task.
mount 192.168.1.9:/test /y is on 192.168.1.4
dd if=/dev/zero of=/y/y bs=1K count=10000000
on 192.168.1.9 systemctl stop nfs-server
on 192.168.1.4
top -p 1849
Code: top -p 1849
top - 03:39:24 up 5 min, 3 users, load average: 0.66, 0.71, 0.39
Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie
%Cpu0 : 0.0 us, 0.0 sy, 0.0 ni, 0.0 id,100.0 wa, 0.0 hi, 0.0 si, 0.0 st
%Cpu1 : 0.0 us, 0.3 sy, 0.0 ni, 99.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1849 root 20 0 108100 616 520 D 0.0 0.0 0:05.24 ddcpu0
0.0 id,100.0 wa ->it means that cpu0 is busy 100%?
then under %CPU is 0.0->?
i expected that cpu0 or cpu1 to run other task until i/o completes.
it seems that cpu0 givea all the cpu cycles to process 1849.