Re: SMP performance degradation with sysbench

Rik van Riel
2007-02-27T14:02:57Z

J.A. Magallón wrote:
> On Mon, 26 Feb 2007 23:31:29 -0500, Rik van Riel <riel@redhat.com> wrote:
>
>> Hiro Yoshioka wrote:

>>> Another question. When the number of threads exceeds the number of
>>> CPU cores, we may get a lot of idle time. Then a workaround of
>>> MySQL is that do not creat threads which exceeds the number
>>> of CPU cores. Is it right?
>> Not really, that would make it impossible for MySQL to
>> handle more simultaneous database queries than the system
>> has CPUs.
>>
>
> I don't know myqsl internals, but you assume one thread per query.
> If its more like Apache, one long living thread for several connections ?

Yes, they are longer lived client connections. One thread
per connection, just like Apache.

> Its the same to answer 4+4 queries than 8 at half the speed, isn't it ?

That still doesn't fix the potential Linux problem that this
benchmark identified.

To clarify: I don't care as much about MySQL performance as
I care about identifying and fixing this potential bug in
Linux.

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