From: Joerg Bruehe (Joerg.BrueheSun.COM)
Date: Tue Dec 16 2008 - 11:49:44 CST

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Hi all,

xufeng wrote:
> Hi fire9,
> Thank you for your reply.
> Do you have some official document on "MySQL 5.0.67 not supporting SMP"?
> If so, would you please give me some info on how to get the smp patches?
>
> Yours,
> Xu Feng
>
>
>
> ________________________________________
> From: fire9 [mailto:fire9dinghgmail.com]
> Sent: 2008?12?16? 11:54
> To: xufeng
> Subject: Re: MySQL 5.0.67 on SMP
>
> hi,
> I think the version is not support SMP.You may use smp patches in this version.
> ? 2008-12-16,??11:44, xufeng ??:
>
>
> Hi
>
> Is there a way to check if my MySQL5.0.67 works well on SMP?
> I have two CPUs with each two cores, and I want to know if MySQL distributes
> loads over the two CPUs.
> System OS: Linux 2.6.9-42.ELsmp
> MySQL Version: 5.0.67
> Intel(R) Xeon(TM) CPU 3.00GHz * 2

that idea of "MySQL 5.0.67 not supporting SMP" is plain wrong:

The MySQL server uses threads internally, one thread per connection, and
any decent operating system (Linux is among them) will distribute the
threads across the available CPUs and cores.

There are just two factors limiting this:

a) "One thread per connection" means that you need multiple connections
   with active commands to profit from your SMP system.
As long as only one applications sends a single stream of commands to
the MySQL server, it cannot use the multiple CPUs / cores.

b) If several of these threads need to access the same resource
   (typically, some data structure), they will synchronize, and only one
thread will proceed immediately while the other(s) block(s).
If that synchronization covers a very large block of code, the
performance of the system will not scale proportionally to the number of
CPUs / cores.

Regards,
Jörg

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Joerg Bruehe, MySQL Build Team, Joerg.BrueheSun.COM
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