I know that this was talked a lot and recently Mark Callaghan also gave a session in MySQL user conference 2008 about the real bottlenecks.
Other day I was testing my thread pool stuff with MySQL 5.1.24 + InnoDB plugin 1.0.1 along with other miscellaneous benchmark tests by making them CPU bound by keep the working set completely in memory to gauge the performance of threads overhead; and on 8-core box InnoDB seems to be doing better than 4-core. And then immediately I started few tests with mysqlslap by keeping complete data set in the buffer pool to get the proper timing on locking overhead.
Here is the comparison of performance on 8-core box with innodb_thread_concurrency is set to 32 and 0 for variable threads on 64-bit Redhat Linux 4 . The same box is used as …[Read more]