Lustre 1.6 Operations Manual

20.3 Debug Support
/proc/sys/lnet/debug
Lustre generates a detailed log of all its operations to aid in debugging by default.
This can affect the performance or speed you achieve with Lustre. Therefore, it is
useful to reduce this overhead by turning down the debug level. Raise the debug
level when you need to collect the logs for debugging problems.
You can verify the debug level used by examining the sysctl that controls the
debugging as shown below:
# sysctl lnet.debug
lnet.debug = -1
In the above example, -1 indicates full debugging; it is a bitmask. You can disable
debugging completely by running the following command on all the concerned
nodes:
# sysctl -w lnet.debug=0
lnet.debug = 0
The appropriate debug level for a production environment is 0x3f0400. It collects
enough high-level information to aid debugging, but it does not cause any serious
performance impact.
You can also verify and change the debug level using the /proc interface in Lustre
as shown below:
# cat /proc/sys/lnet/debug
And change it to:
# echo 0x3f0400 > /proc/sys/lnet/debug
/proc/sys/lnet/subsystem_debug
This controls the debug logs for subsystems (see S_* definitions).
/proc/sys/lnet/debug_path
This indicates the location where debugging symbols should be stored for gdb. The
default is set to /r/tmp/lustre-log-localhost.localdomain.
These values can also be set via sysctl -w lnet.debug={value}
Note – The above entries only exist when Lustre has already been loaded.
Chapter 20 LustreProc 20-25