Author: Robert Hyatt
Date: 07:28:02 11/13/03
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On November 12, 2003 at 20:01:29, Russell Reagan wrote: >One more question. Does making a program NUMA aware cause any performance >penalty when you go back to SMP? IE Would it be at all beneficial for you to >have an SMP version of Crafty _and_ a NUMA version? Or would the same NUMA >version perform equally well on both NUMA and SMP? It should not. It tends to make the code a hair messier. IE before I could malloc() all my split blocks when initializing the engine. Now I have to defer this until a thread is spawned, so that it will be in the local memory of the processor running that particular thread. This is a bit messier. And it can have unwanted side-effects. Suppose you want to zero everything? Can't do it where you do all your normal initialization, as the split blocks don't exist yet. However, making the NUMA changes have not slowed Crafty down one bit, and on NUMA boxes they have made it significantly faster. For this reason, the NUMA changes are just part of the normal SMP stuff. Eugene wrote some windows specific code that will always be executed, but it notices that it is a NUMA box and does the right things there, without affecting things for a non-NUMA box. So we leave this in all the time if SMP is enabled.
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