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50 lines
2.6 KiB
ReStructuredText
50 lines
2.6 KiB
ReStructuredText
What is a mempool?
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------------------
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A memory pool (mempool) is a method for tracking memory consumption. Memory pools represent the memory consumption
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of C++ classes and containers, and they are used to assess memory leaks and other insights around memory usage with
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low overhead. Each memory pool tracks the number of bytes and items it contains. Mempools are statically declared,
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and they serve the purpose of identifying 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``: tracks objects already in the cache pool in order to determine which objects in the pool are
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being accessed
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- ``bluestore_alloc``: 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 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 small writes which are deferred, i.e. first written into RocksDB WAL and later
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flushed to the disk
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- ``bluestore_writing``: accounts for in-flight write buffers
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- ``bluefs``: file-system-like interface; provides just enough functionality to allow RocksDB to store its “files” and share
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the same raw device(s) with 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``: object node (onode) metadata in the 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 accounts for:
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- ``map_t``: used to track raw extents on disk for SharedBlob and 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) extent, pointing to some portion of a blob
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- ``bluestore_blob``: in-memory blob metadata associated cached buffers
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- ``bluestore_shared_blob``: in-memory shared blob state; stores a reference to the set of collections it belongs to
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(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/main/src/include/mempool.h
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