Memory Profiling

Ceph OSD and metadata server daemons can generate heap profiles using tcmalloc. To generate heap profiles, ensure you have google-perftools installed:

sudo apt-get google-perftools

The profiler dumps output to your log file directory (i.e., /var/log/ceph). See Logging and Debugging for details. To view the profiler logs with Google’s performance tools, execute the following:

google-pprof -gv {log-path/filename}

Refer to Google Heap Profiler for additional details.

Once you have the heap profiler installed, start your cluster and begin using the heap profiler. You may enable or disable the heap profiler at runtime, or ensure that it runs continuously. For the following commandline usage, replace {daemon-type} with osd or mds, and replace daemon-id with the OSD number or metadata server letter.

Starting the Profiler

To start the heap profiler, execute the following:

ceph {daemon-type} tell {daemon-id} heap start_profiler

For example:

ceph osd tell 1 heap start_profiler

Printing Stats

To print out statistics, execute the following:

ceph {daemon-type} tell {daemon-id} heap stats

For example:

ceph osd tell 0 heap stats

Note

Printing stats does not require the profiler to be running and does not dump the heap allocation information to a file.

Dumping Heap Information

To dump heap information, execute the following:

ceph {daemon-type} tell {daemon-id} heap dump

For example:

ceph mds tell a heap dump

Note

Dumping heap information only works when the profiler is running.

Releasing Memory

To release memory that tcmalloc has allocated but which is not being used by the Ceph daemon itself, execute the following:

ceph {daemon-type} tell {daemon-id} heap release

For example:

ceph osd tell 2 heap release

Stopping the Profiler

To stop the heap profiler, execute the following:

ceph {daemon-type} tell {daemon-id} heap stop_profiler

For example:

ceph {daemon-type} tell {daemon-id} heap stop_profiler