Question about WCHAN values


 
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# 1  
Old 02-24-2020
Question about WCHAN values

I have a CentOS 8 (3.10) running on VirtualBox 6.0... And I have 2 questions about WCHAN

The 'ps' man page describes WCHAN as:

Quote:
nwchan WCHAN address of the kernel function where the process
is sleeping (use wchan if you want the kernel
function name). Running tasks will display a
dash ('-') in this column.

wchan WCHAN name of the kernel function in which the process
is sleeping, a "-" if the process is running, or
a "*" if the process is multi-threaded and ps is
not displaying threads.

I haven't see the "*" yet, but I'll see a "?" in the output of the "ps" command with regularity. Usually associated with the rcu_sched kernel process, but the "?" does appear for other processes. I haven't found a definition for the "?"... What does it mean?

My 2nd question is about a discrepancy I'm seeing between the output of the 'ps' command and the 'System Monitor' GUI utility. Under the 'ps' command, I'll see several processes in a run state and will have a "-" under WCHAN. Yet under the "System Monitor", those same processes will be in a run state with a WCHAN code of "poll_schedule_timeout". From what I've read this indicates a process is waiting for I/O... Shouldn't these processes be in a sleep state?

Image

Last edited by bodisha; 02-24-2020 at 01:45 PM..
# 2  
Old 02-24-2020
Hi
How to look at a sample line with '?' and headers
Thanks
# 3  
Old 02-24-2020
Thanks for the reply... Here's the output you asked for

Image

Last edited by bodisha; 02-24-2020 at 01:37 PM..
# 4  
Old 02-24-2020
I'm at a loss. It remains to assume either the remote NFS or LXC container
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