Jun
17
2008
The Thread_Concurrency myth
Just a few weeks ago, I found out that thread_concurrency’s purported magical effects at correcting MySQL’s concurrency limitations (especially in 4.1) were something of a myth. It was a post on mysql’s lists that alerted me to this. Apparently it only works on Solaris, Linux’s threading library ignores this parameter completely. This is not to be confused with innodb_thread_concurrency, which is quite useful in controlling the flow of transactions through InnoDB. I think the problem really lies in the fact that the default my.cnf example configs tell us to set thread_concurrency to the number of CPU’s*2. They fail to mention that this only matters on Solaris, though the manual is quite clear.
Continue reading