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+==================
+ 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