Hi Axel, contention on LOCK_open should be improved when we have a decision about MDEV-4956 - Reduce usage of LOCK_open: TABLE_SHARE::tdc.used_tables. I hope your results will revive this task. :)
Regards, Sergey On Thu, Nov 21, 2013 at 06:32:45PM +0100, Axel Schwenke wrote: > Hi, > > I have run another sysbench with in-memory workload to check where we are > with respect to mutex contention. > > The benchmark is sysbench OLTP (using the bzr trunk of sysbench with LUA > support). 10 mio rows in a single table (about 2.5G .ibd file). InnoDB > buffer pool set to 32G and warmed up. > > I have run the test on two different machines. First on our old trusty > facebook2 machine with 8 cores/16 threads in two NUMA zones. Second on the > fat lizard2 machine with 32 cores/64 threads in 4 NUMA zones. > > As expected, the heavy contention of the LOCK_open mutex is more visible on > the bigger machine (I have not done any detailed analysis in this benchmark, > but before while doing benchmarks for MDEV-5081) > > I notice a visible performance gain in MariaDB-10.0 over MariaDB-5.5 at 32 > threads. This is probably due to the work on the InnoDB kernel mutex > (impossible to prove since 5.5 doesn't have mutex instrumentation). At > higher concurrency however the LOCK_open mutex kicks in and performance is > clearly dominated by that mutex alone (it flattens out for all 5.5 and 10.0 > versions of MariaDB) > > The good news is, that 10.0.4, 10.0.5 and 10.0.6 are quite close. There is a > small regression from 10.0.4 to 10.0.5, but IMHO this isn't worth > investigation while the LOCK_open issue is not fixed. > > Attached: diagrams. OpenOffice spreadsheets. > > > XL > _______________________________________________ > Mailing list: https://launchpad.net/~maria-developers > Post to : [email protected] > Unsubscribe : https://launchpad.net/~maria-developers > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
