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Summary: RocksDB does auto-readahead for iterators on noticing more than two sequential reads for a table file if user doesn't provide readahead_size. The readahead starts at 8KB and doubles on every additional read up to max_auto_readahead_size. However at each level, if iterator moves over next file, readahead_size starts again from 8KB. This PR introduces a new ReadOption "adaptive_readahead" which when set true will maintain readahead_size at each level. So when iterator moves from one file to another, new file's readahead_size will continue from previous file's readahead_size instead of scratch. However if reads are not sequential it will fall back to 8KB (default) with no prefetching for that block. 1. If block is found in cache but it was eligible for prefetch (block wasn't in Rocksdb's prefetch buffer), readahead_size will decrease by 8KB. 2. It maintains readahead_size for L1 - Ln levels. Pull Request resolved: https://github.com/facebook/rocksdb/pull/9056 Test Plan: Added new unit tests Ran db_bench for "readseq, seekrandom, seekrandomwhilewriting, readrandom" with --adaptive_readahead=true and there was no regression if new feature is enabled. Reviewed By: anand1976 Differential Revision: D31773640 Pulled By: akankshamahajan15 fbshipit-source-id: 7332d16258b846ae5cea773009195a5af58f8f98 |
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| .. | ||
| cf_options.cc | ||
| cf_options.h | ||
| configurable.cc | ||
| configurable_helper.h | ||
| configurable_test.cc | ||
| configurable_test.h | ||
| customizable.cc | ||
| customizable_test.cc | ||
| db_options.cc | ||
| db_options.h | ||
| options.cc | ||
| options_helper.cc | ||
| options_helper.h | ||
| options_parser.cc | ||
| options_parser.h | ||
| options_settable_test.cc | ||
| options_test.cc | ||