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https://github.com/ceph/ceph
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143 lines
4.6 KiB
ReStructuredText
143 lines
4.6 KiB
ReStructuredText
==================
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Memory Profiling
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==================
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Ceph MON, OSD and MDS can generate heap profiles using
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``tcmalloc``. To generate heap profiles, ensure you have
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``google-perftools`` installed::
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sudo apt-get install google-perftools
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The profiler dumps output to your ``log file`` directory (i.e.,
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``/var/log/ceph``). See `Logging and Debugging`_ for details.
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To view the profiler logs with Google's performance tools, execute the
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following::
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google-pprof --text {path-to-daemon} {log-path/filename}
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For example::
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$ ceph tell osd.0 heap start_profiler
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$ ceph tell osd.0 heap dump
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osd.0 tcmalloc heap stats:------------------------------------------------
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MALLOC: 2632288 ( 2.5 MiB) Bytes in use by application
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MALLOC: + 499712 ( 0.5 MiB) Bytes in page heap freelist
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MALLOC: + 543800 ( 0.5 MiB) Bytes in central cache freelist
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MALLOC: + 327680 ( 0.3 MiB) Bytes in transfer cache freelist
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MALLOC: + 1239400 ( 1.2 MiB) Bytes in thread cache freelists
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MALLOC: + 1142936 ( 1.1 MiB) Bytes in malloc metadata
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MALLOC: ------------
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MALLOC: = 6385816 ( 6.1 MiB) Actual memory used (physical + swap)
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MALLOC: + 0 ( 0.0 MiB) Bytes released to OS (aka unmapped)
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MALLOC: ------------
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MALLOC: = 6385816 ( 6.1 MiB) Virtual address space used
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MALLOC:
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MALLOC: 231 Spans in use
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MALLOC: 56 Thread heaps in use
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MALLOC: 8192 Tcmalloc page size
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------------------------------------------------
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Call ReleaseFreeMemory() to release freelist memory to the OS (via madvise()).
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Bytes released to the OS take up virtual address space but no physical memory.
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$ google-pprof --text \
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/usr/bin/ceph-osd \
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/var/log/ceph/ceph-osd.0.profile.0001.heap
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Total: 3.7 MB
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1.9 51.1% 51.1% 1.9 51.1% ceph::log::Log::create_entry
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1.8 47.3% 98.4% 1.8 47.3% std::string::_Rep::_S_create
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0.0 0.4% 98.9% 0.0 0.6% SimpleMessenger::add_accept_pipe
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0.0 0.4% 99.2% 0.0 0.6% decode_message
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...
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Another heap dump on the same daemon will add another file. It is
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convenient to compare to a previous heap dump to show what has grown
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in the interval. For instance::
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$ google-pprof --text --base out/osd.0.profile.0001.heap \
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ceph-osd out/osd.0.profile.0003.heap
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Total: 0.2 MB
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0.1 50.3% 50.3% 0.1 50.3% ceph::log::Log::create_entry
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0.1 46.6% 96.8% 0.1 46.6% std::string::_Rep::_S_create
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0.0 0.9% 97.7% 0.0 26.1% ReplicatedPG::do_op
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0.0 0.8% 98.5% 0.0 0.8% __gnu_cxx::new_allocator::allocate
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Refer to `Google Heap Profiler`_ for additional details.
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Once you have the heap profiler installed, start your cluster and
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begin using the heap profiler. You may enable or disable the heap
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profiler at runtime, or ensure that it runs continuously. For the
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following commandline usage, replace ``{daemon-type}`` with ``mon``,
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``osd`` or ``mds``, and replace ``{daemon-id}`` with the OSD number or
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the MON or MDS id.
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Starting the Profiler
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---------------------
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To start the heap profiler, execute the following::
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ceph tell {daemon-type}.{daemon-id} heap start_profiler
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For example::
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ceph tell osd.1 heap start_profiler
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Alternatively the profile can be started when the daemon starts
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running if the ``CEPH_HEAP_PROFILER_INIT=true`` variable is found in
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the environment.
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Printing Stats
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--------------
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To print out statistics, execute the following::
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ceph tell {daemon-type}.{daemon-id} heap stats
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For example::
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ceph tell osd.0 heap stats
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.. note:: Printing stats does not require the profiler to be running and does
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not dump the heap allocation information to a file.
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Dumping Heap Information
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------------------------
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To dump heap information, execute the following::
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ceph tell {daemon-type}.{daemon-id} heap dump
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For example::
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ceph tell mds.a heap dump
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.. note:: Dumping heap information only works when the profiler is running.
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Releasing Memory
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----------------
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To release memory that ``tcmalloc`` has allocated but which is not being used by
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the Ceph daemon itself, execute the following::
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ceph tell {daemon-type}{daemon-id} heap release
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For example::
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ceph tell osd.2 heap release
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Stopping the Profiler
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---------------------
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To stop the heap profiler, execute the following::
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ceph tell {daemon-type}.{daemon-id} heap stop_profiler
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For example::
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ceph tell osd.0 heap stop_profiler
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.. _Logging and Debugging: ../log-and-debug
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.. _Google Heap Profiler: http://goog-perftools.sourceforge.net/doc/heap_profiler.html
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