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Re: MariaDB scalability: mutexes


Hi Axel,

thanks for benchmarking it!

On Wed, Feb 26, 2014 at 02:30:50PM +0100, Axel Schwenke wrote:
> Hi Svoj,
> Sergey Vojtovich wrote:
> > I benchmarked various mutexes available to MariaDB.
> > Among other things I noticed that normal mutexes scale better than adaptive.
> > Could you do official benchmarks (patch attached)? It would be nice to also
> > benchmark MySQL-5.6 with thr_lock part of the patch.
> Here are sysbench results for 10.0.8. I added 10.0.7 and MySQL-5.6.10 from
> an earlier run for comparison. The test is sysbench OLTP ro with multiple
> (32) tables.
> The normal mutexes give significantly better throughput. The raw data
> contains also the snapshots from performance schema with the mutex numbers.
> Top mutex is still LOCK_open.
In my benchmark I got like 40% throughput increase whereas in your benchmark
it is like 10%, still not bad.

But you say that there are 32 tables now. It greatly offloads work from
THR_LOCK::mutex (which is per-table) to ... LOCK_open (which is global).
I believe we should see bigger difference for single table load.

Anyway 10% increase looks worthy. I'll try to get this patch into 10.0.9.
Hope it won't sacrifice other loads (according to my microbenchmark it

> I currently run another sysbench OLTP, this time also r/w and with both
> lower and higher concurrency. I added 10.0.8-patched to this, but it won't
> finish before tomorrow.
Great! Please keep me updated.