HyperThreading works well when you have an application that is using different parts of the cpu simultaneously. The key idea is that if you have part of the app doing calculations, and another part copying info from point A to point B the OS can run both threads over the CPU simultaneously because the OS thinks it's asking 1 cpu to do 1 type of operation, and so on. This may work great in a general purpose app like exchange, or maybe any type of DB, but it is only effective when different types of operations/functions are running simultaneously.
HPCC usually is doing the same functions en-masse so their is actually a good chance the additional overhead of "logical processors" can slow things down. For this reason I would just disable the logical processor, and benchmark your app again. If they are close - leave it off. I think most boards give you the option at the BIOS level. Here's the real deal - everything you ever didn't want to know about HyperThreading and how/why they make 2 out of 1: An Introduction to Hyper-Threading Technology in the Intel Xeon Processor Architecture -http://www.dell.com/us/en/esg/topics/power_ps3q02-ht101.htm This article from has lots of benchmarks and better description: A Study of Hyper-Threading in High-Performance Computing Clusters - http://www.dell.com/us/en/esg/topics/power_ps4q02-leng.htm Here's a good comparison/Contrast for when it works, when it doesn't and basic programming constructs with OpenVMS Hyper-Threading and OpenMP - http://www.dell.com/us/en/esg/topics/power_ps4q02-arrian.htm OK, I admit it, if Sterling didn't tell me about it, Dell did - at least when it comes to clusters! Smile, Greg > Message: 3 > Date: Tue, 28 Jan 2003 10:26:23 -0800 > From: Jenny Aquilino <[EMAIL PROTECTED]> > Reply-To: [EMAIL PROTECTED] > To: Sean Dague <[EMAIL PROTECTED]> > CC: [EMAIL PROTECTED] > Subject: Re: [Oscar-users] ganglia question > > > --------------090206070709020108060609 > Content-Type: text/plain; charset=us-ascii; format=flowed > Content-Transfer-Encoding: 7bit > > Hi, > > Could someone explain to me when the OS seeing double causes problems > for Oscar? More specifically, is hyperthreading beneficial in a > clustered environment? I'm not sure how scheduling works in Oscar but > it seems like you would constantly be running into the problem of having > two running jobs being scheduled on the same CPU in a hyperthreaded > environment. > > Currently I have a 6 node, dual Xeon processor cluster that is > hyperthreaded and so I am also seeing 4 CPUs/node instead of 2. > Typically, only one run would be done at a time so in this environment, > could somebody recommend whether to use or not to use hyperthreading? > Thank you very much! > > -Jenny =) > ------------------------------------------------------- This SF.NET email is sponsored by: SourceForge Enterprise Edition + IBM + LinuxWorld = Something 2 See! http://www.vasoftware.com _______________________________________________ Oscar-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/oscar-users
