Part of the InnoDB duties, being an MVCC-implementing storage engine, is to get rid of–purge–the old versions of the records as they become obsolete. In MySQL 5.1 this is done by the master InnoDB thread. Since then, InnoDB has been moving towards the parallelized purge: in MySQL 5.5 there is an option to have a single separate dedicated purge thread and in MySQL 5.6.2 one can have multiple dedicated purge threads.
Percona Server 5.1 supports multiple purge threads too, although using more than one is considered experimental at the moment. Unfortunately this patch hasn’t been ported to Percona Server 5.5 yet.
Let’s test these two implementations and find out what benefits, if any, do the additional purge threads bring.
The test workload makes a long history list and then lets purge