Re: mysql scalability.

[Jeff Roberson]

On Thu, 14 Jun 2007, Sunny Bains wrote:

> Jeff,
>
> Jeff Roberson wrote:
>> Firstly, has anyone examined using pthread standard locks in place of
>> your home-rolled spinlocks?
>
> I assume you mean the InnoDB mutex implementation. I've tested the pthread
> locks under Solaris 10 and it does help there. I'm interested in your
> observations and your comments are most welcome.

I have produced a graph of mysql writes on linux and bsd:

http://people.freebsd.org/~jeff/mysqlwrite.png

This is using the sysbench oltp benchmark.  I see long periods with no 
disk activity and almost no CPU activity where all mysql threads are 
blocked on a condition variable.  This can last for a second or two.  Has 
anyone investigated it?  Is this an understood problem?

The difference between the blue and green lines on FreeBSD is a patch to 
reduce kernel contention related to fcntl().  However, the most 
significant sources of contention by far are in mysql.

Thanks,
Jeff

>
> Regards,
> -sunny
>