Re: [Condor-users] Windows 2000 Server + Condor

["Matt Hope" <matthew.hope@xxxxxxxxx>]

On 4/24/07, Andrey Kaliazin <A.Kaliazin@xxxxxxxxxxx> wrote:
> Hi Andrew
>
> I would not recommend you to turn off hyperthreading on P4 machine -
> you are loosing on performance and multithreading capabilities for nothing.
>
> Much easier to put this line into your condor_config.local file -
>
> COUNT_HYPERTHREAD_CPUS  = FALSE
>
> and restart the condor service.

Couple of things one this.

First: Benchmark your apps with/without hyper threading, make sure you
cover the case where 1 instance per core is running, one instance per
socket is running and one instance only is running. See which is
better, see whether this appears to be memory/cache/disk/network bound
anyway. Measure, measure, measure.
Any advice stating flat out one or the other is bogus. All our stuff
ran better without hyper threading on win 2003 server (only allowing
as many VM's as there were real cores in both cases) so we disable it
in the bios to make the (OS's) scheduler's job easier. but our tasks
tend to suck 100% CPU at all times and have very low cache miss rates.
Note that Hyper-threading implementation changes were made part way
through the Netburst architecture's life cycle and so you may see
different behaviour on different machines.

Second is that COUNT_HYPERTHREADED_CPUS can have issues in some
versions with some operating systems. If it does and you farm is
homogeneous or easy to set up you can explicitly state the number of
VM's you want with NUM_VIRTUAL_MACHINES

Matt