dual cpu's

Seth Mos knuffie at xs4all.nl
Thu Jun 13 17:23:00 CDT 2002

At 12:39 13-6-2002 -0700, Bryce C wrote:
>Hi All,
>I hope this isn't too off-topic or chit-chatty for
>this list, but does anyone have any general comments
>of the effectiveness of dual cpu's in a linux
>environment. The servers are used for apache/mysql/php
>based websites and pretty much active all the time.

Dual CPU's can not make one process go faster. You can however run 2 of 
them at the same speed.
The httpd might be hogging the 1st CPU since someone is fetching a large 
file or running a complicated script and you have a mysql deamon process 
running on CPU 2 which performing a complicated query.

The overall speed is greatly improved but a MySQL deamon will go just as 
fast on either CPU. But you do not have to share the CPU between both the 
httpd and the mysqld at the same time.

>I guess my question is can anyone verify that those
>apps are really going to take advantage of the second
>cpu. I am not too informed about Linux's multiple cpu
>support but I know that on some O.S/apps the second
>CPU is not really used at all?

Earlier FreeBSD systems tended to have that issue. I don't know if it is 
still true or not in -current.

Dual CPU systems tend to work faster under high load because the chance 
that one of the processors has some spare cycles is greatly increased.

It just works. Starting from linux 2.2 and up.


It might just be your lucky day, if you only knew.

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