MariaDB-5.5.21-beta is the first MariaDB release featuring the new thread pool. Oracle offers a commercial thread pool plugin for MySQL Enterprise, but now MariaDB brings a thread pool implementation to the community!
If you are not familiar with the term, please read the Knowledge Base article about it.
The main design goal of the thread pool is to increase the scalability of the MariaDB server with many concurrent connections. In order to test and demonstrate this, I have run the sysbench OLTP RO benchmark with up to 4096 threads to compare the new pool-of-threads and the traditional thread-per-connection scheduler:
- sysbench multi table OLTP, readonly
- 16 tables, totaling 40 mio rows (~10G of data)
- 16G buffer pool – result is independent of disk performance
- mysqld bound to 16 cpu cores, sysbench to the other 8
Read/write OLTP benchmark results will be published as soon as they are available.
Raw benchmark results and the scripts used can be downloaded here
Let me add few more words about binding cpu cores and thread pool configuration.
Sysbench-0.5 which was used for this benchmark, turned out to be quite a cpu hog; especially for high concurrency levels. If both mysqld and sysbench are allowed to run on all cpu cores, they will fight for resources – which will result in artificially bad results with many threads. With 4 cores for sysbench and 20 for mysqld, sysbench itself became the bottleneck. So I ended with 8 cores for sysbench (leaving some room here) and 16 for mysqld.
On UNIX, the MariaDB thread pool normally needs no configuration because it autoconfigures thread-pool-size to the number of cpu cores (this depends on sysconf(3) to implement _SC_NPROCESSORS_ONLN) which is in almost all cases the optimal size. If one binds mysqld to a subset of cpu cores, one should set thread-pool-size manually to the number of cpu cores given to mysqld.