diff options
Diffstat (limited to 'src/ceph/doc/rados/troubleshooting/memory-profiling.rst')
| -rw-r--r-- | src/ceph/doc/rados/troubleshooting/memory-profiling.rst | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/src/ceph/doc/rados/troubleshooting/memory-profiling.rst b/src/ceph/doc/rados/troubleshooting/memory-profiling.rst new file mode 100644 index 0000000..e2396e2 --- /dev/null +++ b/src/ceph/doc/rados/troubleshooting/memory-profiling.rst @@ -0,0 +1,142 @@ +================== + Memory Profiling +================== + +Ceph MON, OSD and MDS can generate heap profiles using +``tcmalloc``. To generate heap profiles, ensure you have +``google-perftools`` installed:: + + sudo apt-get install 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 --text {path-to-daemon} {log-path/filename} + +For example:: + + $ ceph tell osd.0 heap start_profiler + $ ceph tell osd.0 heap dump + osd.0 tcmalloc heap stats:------------------------------------------------ + MALLOC: 2632288 ( 2.5 MiB) Bytes in use by application + MALLOC: + 499712 ( 0.5 MiB) Bytes in page heap freelist + MALLOC: + 543800 ( 0.5 MiB) Bytes in central cache freelist + MALLOC: + 327680 ( 0.3 MiB) Bytes in transfer cache freelist + MALLOC: + 1239400 ( 1.2 MiB) Bytes in thread cache freelists + MALLOC: + 1142936 ( 1.1 MiB) Bytes in malloc metadata + MALLOC: ------------ + MALLOC: = 6385816 ( 6.1 MiB) Actual memory used (physical + swap) + MALLOC: + 0 ( 0.0 MiB) Bytes released to OS (aka unmapped) + MALLOC: ------------ + MALLOC: = 6385816 ( 6.1 MiB) Virtual address space used + MALLOC: + MALLOC: 231 Spans in use + MALLOC: 56 Thread heaps in use + MALLOC: 8192 Tcmalloc page size + ------------------------------------------------ + Call ReleaseFreeMemory() to release freelist memory to the OS (via madvise()). + Bytes released to the OS take up virtual address space but no physical memory. + $ google-pprof --text \ + /usr/bin/ceph-osd \ + /var/log/ceph/ceph-osd.0.profile.0001.heap + Total: 3.7 MB + 1.9 51.1% 51.1% 1.9 51.1% ceph::log::Log::create_entry + 1.8 47.3% 98.4% 1.8 47.3% std::string::_Rep::_S_create + 0.0 0.4% 98.9% 0.0 0.6% SimpleMessenger::add_accept_pipe + 0.0 0.4% 99.2% 0.0 0.6% decode_message + ... + +Another heap dump on the same daemon will add another file. It is +convenient to compare to a previous heap dump to show what has grown +in the interval. For instance:: + + $ google-pprof --text --base out/osd.0.profile.0001.heap \ + ceph-osd out/osd.0.profile.0003.heap + Total: 0.2 MB + 0.1 50.3% 50.3% 0.1 50.3% ceph::log::Log::create_entry + 0.1 46.6% 96.8% 0.1 46.6% std::string::_Rep::_S_create + 0.0 0.9% 97.7% 0.0 26.1% ReplicatedPG::do_op + 0.0 0.8% 98.5% 0.0 0.8% __gnu_cxx::new_allocator::allocate + +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 ``mon``, +``osd`` or ``mds``, and replace ``{daemon-id}`` with the OSD number or +the MON or MDS id. + + +Starting the Profiler +--------------------- + +To start the heap profiler, execute the following:: + + ceph tell {daemon-type}.{daemon-id} heap start_profiler + +For example:: + + ceph tell osd.1 heap start_profiler + +Alternatively the profile can be started when the daemon starts +running if the ``CEPH_HEAP_PROFILER_INIT=true`` variable is found in +the environment. + +Printing Stats +-------------- + +To print out statistics, execute the following:: + + ceph tell {daemon-type}.{daemon-id} heap stats + +For example:: + + ceph tell osd.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 tell {daemon-type}.{daemon-id} heap dump + +For example:: + + ceph tell mds.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 tell {daemon-type}{daemon-id} heap release + +For example:: + + ceph tell osd.2 heap release + + +Stopping the Profiler +--------------------- + +To stop the heap profiler, execute the following:: + + ceph tell {daemon-type}.{daemon-id} heap stop_profiler + +For example:: + + ceph tell osd.0 heap stop_profiler + +.. _Logging and Debugging: ../log-and-debug +.. _Google Heap Profiler: http://goog-perftools.sourceforge.net/doc/heap_profiler.html |