blade servers (was Re: [Bioclusters] Any experiences with these guys? reeks)

[Tim Cutts]

On 04-Nov-03, Goran Ceric wrote:
> In my experience, HT helps the most if you run several competing 
> applications. It's not that beneficial to a single multithreaded 
> application unless the threads are complimentary to each other. It all 
> depends on what you want to run. If you run code that's 100% FP, I think 
> you better turn HT off. Sometimes you have to try it with and without HT 
> to see what works better. And yes, Tim is right, current kernels don't 
> schedule smartly to logical CPUs.

I think you're right if you're overcommitting CPUs (i.e. your load
average is more than than the number of CPUs in the box), but we
configure LSF carefully to arrange one single threaded job per CPU, and
never overcommit the CPUs (unless the users do something silly, of
course!)

Tim

-- 
Dr Tim Cutts
Informatics Systems Group
Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA, UK