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doc/dev: define what mempools we use in bluestore Signed-off-by: Anthony D'Atri <anthony.datri@gmail.com>
57 lines
2.7 KiB
ReStructuredText
57 lines
2.7 KiB
ReStructuredText
What is a mempool?
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------------------
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A memory pool is a method for accounting the consumption of memory of
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Memory pools (mempools) show the details of memory consumption of C++ classes and containers, which can then be used to assess memory leaks, and other insights around memory usage with low overhead.
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Each memory pool tracks the number of bytes and items it contains.
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Memory pools are statically declared and serves the purpose of identifying
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memory related checks in BlueStore.
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Some common mempools that we can track
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--------------------------------------
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- ``bloom_filter``: Ceph uses bloom filters to account for tracking objects already
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in the cache pool, in order to determine which objects in the pool are being
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accessed.
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- ``bluestore_alloc``: It accounts for actual allocations done by an allocator.
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- ``bluestore_inline_bl``: measures encoded length of an inline buffer.
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- ``bluestore_fsck``: file system consistency check for BlueStore metadata, helps in
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tracking and debugging during OSD repairs.
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- ``bluestore_txc``: accounts for committed transactions counter.
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- ``bluestore_writing_deferred``: measures those small writes which are deferred
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i.e. first written into RocksDB WAL and later flushed to disk.
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- ``bluestore_writing``: TBD
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- ``bluefs``: file-system-like interface that provides just enough functionality to
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allow RocksDB to store its “files” and share the same raw device(s) with
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BlueStore.
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- ``buffer_anon``: stores arbitrary buffer data.
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- ``buffer_meta``: all the metadata associated with buffer anon buffers.
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- ``bluestore_cache_data``: mempool for writing and writing deferred.
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- ``bluestore_cache_onode``: meta information of object node stored directed in
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bluestore cache.
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- ``bluestore_cache_meta``: key under PREFIX_OBJ where we are stored.
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- ``bluestore_cache_other``: right now account's for
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- ``map_t``: we use it to track raw extents on disk for SharedBlob. We also use
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it for the in-memory Blob with the blob namespace.
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- ``coll_map``: collections_map
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- ``csum_data``: checksum data
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- ``bluestore_cache_buffer``: accounts for buffer cache shards.
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- ``bluestore_extent``: a logical as well as physical extents, pointing to (some
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portion of) a blob.
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- ``bluestore_blob``: in-memory blob metadata and associated cached buffers.
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- ``bluestore_shared_blob``: in memory shared blob state, stores reference of set of
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collections it is part of (includes cached buffers).
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- ``bluefs_file_reader``: accounts for bluefs file reader buffer.
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- ``bluefs_file_writer``: accounts for bluefs file writer buffer.
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Check mempools usage
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~~~~~~~~~~~~~~~~~~~~
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Command to see BlueStore memory allocation in these mempools::
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$ ceph daemon osd.NNN dump_mempools
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.. note:: see more:
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https://github.com/ceph/ceph/blob/master/src/include/mempool.h
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