dual vs single core opteron 100's

[Lars Tunkrans]

Ken Gunderson wrote:

>On Tue, 24 Jan 2006 19:09:22 +0100
>Lars Tunkrans <lars.tunkrans at bredband.net> wrote:
>
>  
>
>>Ken Gunderson wrote:
>>
>>    
>>
>>>Greets Everyone:
>>>
>>>I was getting into a discussion the other day about this and decided to
>>>see what the FBSD amd64 gurus had to say about it.  Given approximately
>>>equal cost of, for example, a single core Opteron150 (2.4GHz) and a
>>>dual core Opteron165 (1.8GHz) under what kind of situations would
>>>one be preferred over the other?  
>>>
>>>      
>>>
>>The DUAL core will be prefferd  for Webservers, Application servers,   
>>and databases
>>that  are multithreaded  and transaction oriented.
>>    
>>
>
>That was his point- precious few of these exist in FOSS, e.g. X,
>anything Python based, etc.  I thought, even so, the dual cores will
>benefit at higher concurrency (just not quite as good a dual CPU).
>Then enter his comment that "context switching on FBSD sucks..
>Blah, blah, blah..."
>  
>

  Really ?     your  friend should know  that  when you deploy  
apache/tomcat
you always    start  several instance  of the httpd   servers.  Even  if 
they
individually where completly  singel threaded,  starting the normal 5 to 
10  httpd's 
on a dualcore  would double  the  throughput, ( not the performance )  
compared to a single core CPU,
provided you dont have other bottlenecks in the architecure, like too 
few  diskdrives, aso.
And  provided  that you get enough http requests to use the added 
processing power.
Context switching will take the same time per-proccess regardless of the 
number of CPU's

Remember that  additional CPU's  dont imply that things work faster.  
Only that you can
do more OF THEM  concurrently.  Throughput increases,  not individual 
task  performance.


//Lars