mysql scaling questions

Kris Kennaway kris at
Sun Dec 30 06:30:55 PST 2007

Gergely CZUCZY wrote:

>>>> Still waiting for your sysbench command lines :)
>>> There were 2 scripts and a sources file with options:
>>> basicall that's everything. I know it's a but complex, but this was all behind it.
>> OK, that was very important since you're changing defaults.
> For different configurations, yes. But every test is heterogenous.

I meant important from the point of view of others being able to repeat 
your tests.

>> It looks like myisam is doing huge numbers of concurrent reads of the same file which is running into exclusive locking in the kernel 
>> (vnode interlock and lockbuilder mtxpool).  Does it not do any caching of the data in userspace but relies on querying into the kernel 
>> every time? innodb doesn't have this behaviour.
> Sorry, but was this a rethorical kind of question, or was this addressed to me? :)
> If the later, then how do I find this out?

It's a general question.  It looks like myisam either has a design 
deficiency in this regard or it has poor defaults.  If it can be made to 
improve caching of the data in userland then performance should improve.


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