Lustre 1.6 Operations Manual

4. If you already have a debug log saved to disk (likely from a crash), to filter a
log on disk:
lctl > debug_file [output filename]
During the debug session, you can add markers or breaks to the log for any
reason:
lctl > mark [marker text]
The marker text defaults to the current date and time in the debug log (similar to
the example shown below):
DEBUG MARKER: Tue Mar 5 16:06:44 EST 2002
5. To completely flush the kernel debug buffer:
lctl > clear
Note – Debug messages displayed with lctl are also subject to the kernel debug
masks; the filters are additive.
23.2.4 Finding Memory Leaks
Memory leaks can occur in a code where you allocate a memory, but forget to free it
when it becomes non-essential. You can use the leak_finder.pl tool to find
memory leaks. Before running this program, you must turn on the debugging to
collect all malloc and free entries. Run:
sysctl -w lnet.debug=+malloc
Dump the log into a user-specified log file using lctl (as shown in The lctl Tool). Run
the leak finder on the newly-created log dump:
perl leak_finder.pl
The output is:
malloced 8bytes at a3116744 (called pathcopy)
(lprocfs_status.c:lprocfs_add_vars:80)
freed 8bytes at a3116744 (called pathcopy)
(lprocfs_status.c:lprocfs_add_vars:80)
The tool displays the following output to show the leaks found:
Leak:32bytes allocated at a23a8fc
(service.c:ptlrpc_init_svc:144,debug file line 241)
23-8 Lustre 1.6 Operations Manual • September 2008