--- /dev/null
+==================
+ 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
Code Review / stor4nfv.git / blobdiff