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Lustre Debugging for Developers
The procedures below may be useful to developers debugging Lustre code.
Adding Debugging to the Source Code
The debug infrastructure provides a number of macros that can be used in Lustre™ source code to aid in debugging or reporting serious errors.
To use these macros, you will need to set the DEBUG_SUBSYSTEM variable at the top of the file to do what?? as shown below:
#define DEBUG_SUBSYSTEM S_PORTALS
A list of available macros with descriptions is provided in see Section 23.2.8: Adding Debugging to the Lustre Source Code in the Lustre Operations Manual.
Ptlrpc Request History ...Requesting a service history using prlrpc?
Each service maintains a request history, which can be useful for first occurrence troubleshooting.
PTLRPC An RPC protocol layered on LNET. This protocol deals with stateful servers and has exactly -once semantics and built in support for recovery.
prlrpc is listed as a subsystem in the Lustre Debug Messages section.
For more information about how to use prlrpc, see Section 23.5: Ptlrpc Request History in the Lustre Operations Manual.
Using lightweight tracing (LWT) for debugging
Lustre offers a lightweight tracing facility called LWT that can be useful for debugging difficult problems. It prints fixed size requests into a buffer and is much faster than LDEBUG.
LWT trace-based records that are dumped contain:
- Current CPU
- Process counter
- Pointer to file
- Pointer to line in the file
- Four void * pointers
An lctl command dumps the logs to files.
Finding memory leaks using leak_finder.pl
Memory leaks can occur in code when memory has been allocated and then not freed once it is no longer required. The leak_finder.pl program provides a way to find memory leaks.
For details, see Section 23.2.4: Finding Memory Leaks in the Lustre Operations Manual.
