General Mysql Performance Question

Paul A. Procacci pprocacci at
Fri Aug 29 08:00:26 UTC 2008

Kris Kennaway wrote:
> Paul A. Procacci wrote:
>> My question is in reference to the 1st and 2nd graphs on this page.  
>> While testing the performance of the databases given in this graph, 
>> the one thing that sticks out is that when Mysql uses the myisam 
>> engine with the ULE schedular, performance drops quite considerably 
>> regardless of mysql version.  The clearly shows ULE to perform worst 
>> at higher work loads than 4BSD, at least in this one example.
>> Now, I read that lockmgr code is still a work in progress, but I'm 
>> unsure if that applies specifically to this specific problem that I'm 
>> providing.  What I'm hoping for quite frankly is a "yes, this is 
>> because...." type of response.
>> This isn't a problem per se, but rather a curiosity type of question.
> myisam has huge lock contention, so probably ULE is more efficiently 
> scheduling the processes and increasing contention yet further, 
> leading to a net drop of performance.  That kind of thing is fairly 
> common when you have a workload with high contention; if you improve 
> performance at one bottleneck the performance at a later bottleneck 
> can get worse. Performance will still be better on other workloads, or 
> when further work improves the other bottlenecks.
> Kris
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Thanks for your prompt response.  I was aware that myisam had pretty 
huge lock contention, but didn't think ULE, because it's doing it's job 
better, is actually making things worse.

I appreciate your insight.


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