On 14-Jul-09, at 5:14 PM, Robert Kubrick wrote:
Jody,
Just to make sure, you did set processor affinity during your test
right?
I'm not sure what that means in the context of OS X.
Hyperthreading was turned on.
Cheers, Jody
On Jul 13, 2009, at 9:28 PM, Klymak Jody wrote:
Hi Robert,
I got inspired by your question to run a few more tests. They are
crude, and I don't have actual cpu timing information because of a
library mismatch. However:
Setup:
Xserve, 2x2.26 GHz Quad-core Intel Xeon
6.0 Gb memory 1067 MHz DDR3
Mac OS X 10.5.6
Nodes are connected with a dedicated gigabit ethernet switch.
I'm running the MITgcm, a nonhydrostatic global circulation model.
The grid size is modest: 10x150x1600, so bear that in mind.
Message passing is on the dimension that is 150x10, and typically
is 3 grid cells in either direction. I'm not sure how many
variables are passed, but I would guess on the order of 24.
I turned off all the I/O I knew of to reduce disk latency.
1 node: 8 processes: 54 minutes
1 node: 16 processes: 40 minutes (oversubscribed)
2 nodes, 16 processes: 29 minutes
So, oversubscribing was faster (in this case), but it didn't double
the speed. Certainly spreading the load to another node was much
faster.
I haven't had a chance to implement Warner's suggestion of turning
hyperthreading off to see what affect that has on the speed.
Cheers, Jody
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