maria-developers team mailing list archive

[Sergey Vojtovich <svoj@xxxxxxxxxxx>]

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







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