628786ed14
Summary: We have observed an increase in CPU load caused by frequent calls to `ColumnFamilyData::InstallSuperVersion` from `DBImpl::TrimMemtableHistory` when using `max_write_buffer_size_to_maintain` to limit the amount of memtable history maintained for transaction conflict checking. Part of the issue is that trimming can potentially be scheduled even if there is no memtable history. The patch adds a check that fixes this. See also https://github.com/facebook/rocksdb/pull/6169. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6177 Test Plan: Compared `perf` output for ``` ./db_bench -benchmarks=randomtransaction -optimistic_transaction_db=1 -statistics -stats_interval_seconds=1 -duration=90 -num=500000 --max_write_buffer_size_to_maintain=16000000 --transaction_set_snapshot=1 --threads=32 ``` before and after the change. There is a significant reduction for the call chain `rocksdb::DBImpl::TrimMemtableHistory` -> `rocksdb::ColumnFamilyData::InstallSuperVersion` -> `rocksdb::ThreadLocalPtr::StaticMeta::Scrape` even without https://github.com/facebook/rocksdb/pull/6169. Differential Revision: D19057445 Pulled By: ltamasi fbshipit-source-id: dff81882d7b280e17eda7d9b072a2d4882c50f79
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 especially 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/
License
RocksDB is dual-licensed under both the GPLv2 (found in the COPYING file in the root directory) and Apache 2.0 License (found in the LICENSE.Apache file in the root directory). You may select, at your option, one of the above-listed licenses.