7c95868378
Summary: The global atomics we previously used for tickers had poor cache performance since they were typically updated from different threads, causing frequent invalidations. In this diff, - recordTick() updates a local ticker value specific to the thread in which it was called - When a thread exits, its local ticker value is added into merged_sum - getTickerCount() returns the sum of all threads' local ticker values and the merged_sum - setTickerCount() resets all threads' local ticker values and sets merged_sum to the value provided by the caller. In a next diff I will make a similar change for histogram stats. Test Plan: before: $ TEST_TMPDIR=/dev/shm/ perf record -g ./db_bench --benchmarks=readwhilewriting --statistics --num=1000000 --use_existing_db --threads=64 --cache_size=250000000 --compression_type=lz4 $ perf report -g --stdio | grep recordTick 7.59% db_bench db_bench [.] rocksdb::StatisticsImpl::recordTick ... after: $ TEST_TMPDIR=/dev/shm/ perf record -g ./db_bench --benchmarks=readwhilewriting --statistics --num=1000000 --use_existing_db --threads=64 --cache_size=250000000 --compression_type=lz4 $ perf report -g --stdio | grep recordTick 1.46% db_bench db_bench [.] rocksdb::StatisticsImpl::recordTick ... Reviewers: kradhakrishnan, MarkCallaghan, IslamAbdelRahman, sdong Reviewed By: sdong Subscribers: yiwu, andrewkr, dhruba, leveldb Differential Revision: https://reviews.facebook.net/D62337
RocksDB: A Persistent Key-Value Store for Flash and RAM Storage
RocksDB is developed and maintained by Facebook Database Engineering Team. It is built on earlier work on LevelDB by Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com)
This code is a library that forms the core building block for a fast key value server, especially suited for storing data on flash drives. It has a Log-Structured-Merge-Database (LSM) design with flexible tradeoffs between Write-Amplification-Factor (WAF), Read-Amplification-Factor (RAF) and Space-Amplification-Factor (SAF). It has multi-threaded compactions, making it specially suitable for storing multiple terabytes of data in a single database.
Start with example usage here: https://github.com/facebook/rocksdb/tree/master/examples
See the github wiki for more explanation.
The public interface is in include/. Callers should not include or
rely on the details of any other header files in this package. Those
internal APIs may be changed without warning.
Design discussions are conducted in https://www.facebook.com/groups/rocksdb.dev/