Upgrade to dual-core (Pentium D) processor - Does it worth it?

[Tobias P. Santos]

Hello!

We have a server running FreeBSD 5.4 i386 (which we plan to upgrade to
6.1) with a single Pentium 4 2.8GHz processor without SMP kernel.
This machine basically serves web pages that may or may not use MySQL
server (also run in this server).
Usually, we have low usage and load average is ~ 0.2 which is ok, but
sometimes, one single process (e.g., mysqld) begins to use all CPU
cycles, loading up the system and leading the other smaller processes
(in terms of CPU usage) to have a high response time.
As this server's motherboard doesn't support an additional processor, we
are wondering whether a Pentium D processor (830) might help to minimize
this problem.
In our understanding, one core would be busy with mysqld for example,
while the other one would be free to handle other processes like httpd
and serve pages that don't even need mysql resources.
Is this correct? Did someone have similiar (successful or unsuccessful)
experiences?

Thank you in advance,
Tobias.

[Mike Sturdee]

Here's an article you might be interested in..

http://www.overclockers.com.au/article.php?id=489587

-Mike

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[Eric Anderson]

This isn't a clear cut yes/no situation I don't think, but for mysqld,
there's a lot of tuning you could probably do to make the cpu time drop
and free up more cycles for other processes. There's been discussions
in the past on this list about mysql, but if you have already done all
the optimizations that you can with mysql (with indexes and such for
instance), then the extra processor would definitely allow the other
non-database blocked web pages to be served, as long as you aren't
actually IO bound somewhere. I don't know how much memory you have in
the current machine, but adding more might be a good quick upgrade (that
is fairly cheap probably).

Eric

--
------------------------------------------------------------------------
Eric Anderson Sr. Systems Administrator Centaur Technology
Anything that works is better than anything that doesn't.
------------------------------------------------------------------------

[Charles Swiger]

On Jul 14, 2006, at 12:52 PM, Tobias P. Santos wrote:
> As this server's motherboard doesn't support an additional
> processor, we are wondering whether a Pentium D processor (830)
> might help to minimize this problem.
> In our understanding, one core would be busy with mysqld for
> example, while the other one would be free to handle other
> processes like httpd and serve pages that don't even need mysql
> resources.
> Is this correct? Did someone have similiar (successful or
> unsuccessful) experiences?

Yes, in particular, the preforking design that Apache uses
distributes very well amoungst multiple CPUs. There is some overhead
from using SMP, you might get better performance by separating your
workload into two machines, one dedicated to Apache and one dedicated
to your MySQL database, but upgrading to a dual-core CPU is cheaper...

--
-Chuck