MyRocks: Server sits at 100% CPU utilization after starting up, never goes down

[Rahul Vaidya]

I have a set of databases whos tables are all in MYROCKS that are ~ 500GB on disk, but they're running on small cloud servers.   Whenever MariaDB starts up, the CPU spikes up to 100% and stays there.  Previously, I had been using TokuDB, and I only started experiencing this when I converted the tables to MYROCKS.

Query performance on all of these tables is impacted, which is why I am considering  converting all of these tables to InnoDB to mitigate the issue in the short term.  However, I ultimately don't know where the problem lies.

Is there a way of disabling compaction / other RocksDB background jobs so I can see if RocksDB is indeed causing my issues?

[Matsunobu Yoshinori]

Could you show CPU profiles (e.g. Linux Perf) telling where it spends most of the CPU time?

There are also status variables showing total compaction bytes (rocksdb_compact_write_bytes).

SHOW ENGINE ROCKSDB STATUS shows column family statistics.

MyRocks has a global variable to tune background number of compactions and flush (rocksdb_max_background_jobs).

rocksdb_max_background_jobs needs to be smaller if you have very few CPU cores.

- Yoshinori