Summary:
PR https://github.com/facebook/rocksdb/issues/5298 (and subsequent related patches) unintentionally changed the
semantics of cache_index_and_filter_blocks: historically, this option
only affected the main index/filter block; with the changes, it affects
index/filter partitions as well. This can cause performance issues when
cache_index_and_filter_blocks is false since in this case, partitions are
neither cached nor preloaded (i.e. they are loaded on demand upon each
access). The patch reverts to the earlier behavior, that is, partitions
are cached similarly to data blocks regardless of the value of the above
option.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5705
Test Plan:
make check
./db_bench -benchmarks=fillrandom --statistics --stats_interval_seconds=1 --duration=30 --num=500000000 --bloom_bits=20 --partition_index_and_filters=true --cache_index_and_filter_blocks=false
./db_bench -benchmarks=readrandom --use_existing_db --statistics --stats_interval_seconds=1 --duration=10 --num=500000000 --bloom_bits=20 --partition_index_and_filters=true --cache_index_and_filter_blocks=false --cache_size=8000000000
Relevant statistics from the readrandom benchmark with the old code:
rocksdb.block.cache.index.miss COUNT : 0
rocksdb.block.cache.index.hit COUNT : 0
rocksdb.block.cache.index.add COUNT : 0
rocksdb.block.cache.index.bytes.insert COUNT : 0
rocksdb.block.cache.index.bytes.evict COUNT : 0
rocksdb.block.cache.filter.miss COUNT : 0
rocksdb.block.cache.filter.hit COUNT : 0
rocksdb.block.cache.filter.add COUNT : 0
rocksdb.block.cache.filter.bytes.insert COUNT : 0
rocksdb.block.cache.filter.bytes.evict COUNT : 0
With the new code:
rocksdb.block.cache.index.miss COUNT : 2500
rocksdb.block.cache.index.hit COUNT : 42696
rocksdb.block.cache.index.add COUNT : 2500
rocksdb.block.cache.index.bytes.insert COUNT : 4050048
rocksdb.block.cache.index.bytes.evict COUNT : 0
rocksdb.block.cache.filter.miss COUNT : 2500
rocksdb.block.cache.filter.hit COUNT : 4550493
rocksdb.block.cache.filter.add COUNT : 2500
rocksdb.block.cache.filter.bytes.insert COUNT : 10331040
rocksdb.block.cache.filter.bytes.evict COUNT : 0
Differential Revision: D16817382
Pulled By: ltamasi
fbshipit-source-id: 28a516b0da1f041a03313e0b70b28cf5cf205d00
d92a59b6f2