Analysing processes in D state (uninterruptable sleep)

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Environment

SUSE Linux Enterprise Server 11 SP2
SUSE Linux Enterprise Server 11 SP11
SUSE Linux Enterprise Server 11

Situation

One or several processes are in D state, also called uninterruptable sleep. In some cases this doesn't affect the system's performance or behavior, but sometimes it leads to high load and/or bad performance.

Resolution

There are two ways to find more about the processes in D state.

1. ps -eo ppid,pid,user,stat,pcpu,comm,wchan:32
This prints a list of all processes where in the last column either a '-' is displayed when the process is running or the name of the kernel function in which the process is sleeping if the process is currently sleeping. This includes also processes which are interruptible. Processes that are in uninterruptible sleep can be determined via the fourth column which would then show a D.

2. echo w > /proc/sysrq-trigger
This command produces a report and a list of all processes in D state and a full kernel stack trace to /var/log/messages. This shows much more information than the first option described above.

Disclaimer

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