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If there are a lot of processes in D state in your system, then something is wrong with it.
What is "D state" and process state in generally? A process in Linux can be in several states: runing state,
sleeping state and others. Running process runs on a CPU just now, Sleeping process waits for its turn on CPU
or for some other event. Using ps command you can obtain information about state of each process in the system: STAT column shows that:
<pre>
[root@dhcp0-56 ovz-utils]# ps a
PID TTY STAT TIME COMMAND
4975 tty1 Ss+ 0:00 /sbin/mingetty tty1
4976 tty2 Ss+ 0:00 /sbin/mingetty tty2
6202 pts/0 Ss+ 0:01 -bash
10312 pts/1 Ss 0:00 -bash
639 pts/1 R+ 0:00 ps a
</pre>
First big '''S''' stands for Sleeping, '''R''' stands for runing
("+" means that the process is foreground and small "s" means that the process is session leader, but it isn't relevant in our discussion).
D state occurs then the process is in uninterruptable disk sleep. This state is bad, because you can't do anything with the process in D state.
Fortunately, process normally remains in such state not for long.
If you have a heap of D state processes than some logic in system is disrupt. The very important thing then is to determine,
where this unlucky sleep occurs. It is easy to do with ps command with ''l'' option. WCHAN column shows the name of the kernel function where
the process is sleeping:
<pre>
[root@dhcp0-56 ~]# ps axl | grep D
F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND
vass 13478 7.2 0.0 1732 624 pts/1 D+ 17:36 0:00 find ./
</pre>
Then you have problem with D state processes always attach this information to the report, that you send to developers.
[[Category: Troubleshooting]]
What is "D state" and process state in generally? A process in Linux can be in several states: runing state,
sleeping state and others. Running process runs on a CPU just now, Sleeping process waits for its turn on CPU
or for some other event. Using ps command you can obtain information about state of each process in the system: STAT column shows that:
<pre>
[root@dhcp0-56 ovz-utils]# ps a
PID TTY STAT TIME COMMAND
4975 tty1 Ss+ 0:00 /sbin/mingetty tty1
4976 tty2 Ss+ 0:00 /sbin/mingetty tty2
6202 pts/0 Ss+ 0:01 -bash
10312 pts/1 Ss 0:00 -bash
639 pts/1 R+ 0:00 ps a
</pre>
First big '''S''' stands for Sleeping, '''R''' stands for runing
("+" means that the process is foreground and small "s" means that the process is session leader, but it isn't relevant in our discussion).
D state occurs then the process is in uninterruptable disk sleep. This state is bad, because you can't do anything with the process in D state.
Fortunately, process normally remains in such state not for long.
If you have a heap of D state processes than some logic in system is disrupt. The very important thing then is to determine,
where this unlucky sleep occurs. It is easy to do with ps command with ''l'' option. WCHAN column shows the name of the kernel function where
the process is sleeping:
<pre>
[root@dhcp0-56 ~]# ps axl | grep D
F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND
vass 13478 7.2 0.0 1732 624 pts/1 D+ 17:36 0:00 find ./
</pre>
Then you have problem with D state processes always attach this information to the report, that you send to developers.
[[Category: Troubleshooting]]
