Summary:
Some usage of vector memtable is bottlenecked in the memtable insertion path when using multiple writers. This PR adds support for concurrent writes for the vector memtable. The updates from each concurrent writer are buffered in a thread local vector. When a writer is done, MemTable::BatchPostProcess() is called to flush the thread local updates to the main vector. TSAN test and function comment suggest that ApproximateMemoryUsage() needs to be thread-safe, so its implementation is updated to provide thread-safe access.
Together with unordered_write, benchmark shows much improved insertion throughput.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/13675
Test Plan:
- new unit test
- enabled some coverage of vector memtable in stress test
- Performance benchmark: benchmarked memtable insertion performance with by running fillrandom 20 times
- Compare branch and main performance with one thread and write batch size 100:
- main: 4896888.950 ops/sec
- branch: 4923366.350 ops/sec
- Benchmark this branch by configuring different threads, allow_concurrent_memtable_write, and unordered_write. Performance ratio is computed as current ops/sec divided by ops/sec at 1 thread with the same options.
allow_concurrent | unordered_write | Threads | ops/sec | Performance Ratio
-- | -- | -- | -- | --
0 | 0 | 1 | 4923367 | 1.0
0 | 0 | 2 | 5215640 | 1.1
0 | 0 | 4 | 5588510 | 1.1
0 | 0 | 8 | 6077525 | 1.2
1 | 0 | 1 | 4919060 | 1.0
1 | 0 | 2 | 5821922 | 1.2
1 | 0 | 4 | 7850395 | 1.6
1 | 0 | 8 | 10516600 | 2.1
1 | 1 | 1 | 5050004 | 1.0
1 | 1 | 2 | 8489834 | 1.7
1 | 1 | 4 | 14439513 | 2.9
1 | 1 | 8 | 21538098 | 4.3
```
mkdir -p /tmp/bench_$1
export TEST_TMPDIR=/tmp/bench_$1
memtablerep_value=${6:-vector}
(for I in $(seq 1 $2)
do
/data/users/changyubi/vscode-root/rocksdb/$1 --benchmarks=fillrandom --seed=1722808058 --write_buffer_size=67108864 --min_write_buffer_number_to_merge=1000 --max_write_buffer_number=1000 --enable_pipelined_write=0 --memtablerep=$memtablerep_value --disable_auto_compactions=1 --disable_wal=1 --avoid_flush_during_shutdown=1 --allow_concurrent_memtable_write=${5:-0} --unordered_write=$4 --batch_size=1 --threads=$3 2>&1 | grep "fillrandom"
done;) | awk '{ t += $5; c++; print } END { printf ("%9.3f\n", 1.0 * t / c) }';
```
Reviewed By: pdillinger
Differential Revision: D76641755
Pulled By: cbi42
fbshipit-source-id: c107ba42749855ad4fd1f52491eb93900757542e
c8aafdba33