CPU overhead from lock_tables is about 2X larger for MyRocks than for InnoDB #1484
Description
I am looking at flamegraphs from sysbench with a cached database and 1 client. A common problem I see is that the percentage of samples that lock_tables (and its callees) accounts for is ~2X larger in MyRocks than in InnoDB with simple microbenchmarks.
Using results from the insert microbenchmark, for InnoDB
1.58% -> lock_tables
1.13% -> mysql_lock_tables
0.35% -> get_lock-data
0.45% -> handler::ha_external_lock
And from MyRocks
2.89% -> lock_tables
2.51% -> mysql_lock_tables
2.09% -> handler::ha_external_lock
1.81% -> ha_rocksdb::external_lock
1.31% -> myrocks::get_or_create_tx
1.17% -> Rdb_transaction_impl::start_tx
0.91% -> rocksdb::WriteCommittedTxnDB::BeginTransaction
0.80% -> rocksdb::PessimisticTransaction::Reinitialize
The flamegraphs are attached:
