Author: Russell Reagan
Date: 16:07:32 11/12/03
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On November 12, 2003 at 18:09:31, Robert Hyatt wrote: >You have to jump through some hoops, and also hope that the O/S helps. On >windows, Eugene is using the set processor affinity mechanism to lock a >thread to a particular CPU. Does this have to be done manually or is there an API call to do this (Windows or Linux)? >The idea is that you have a CPU connected to a "router" which is >connected to the local memory for that CPU, plus the router is >connected to other routers for other processors. Your local router can >access your local memory and give it to you quickly. To access memory on >other processors requires that you ask your router for the memory, and it >has to ask a router it can reach to either give it the value or forward the >request on to a router that is closer, until the request finally arrives >at the router connected to the local memory. It's all those "hops" that >kill performance. So you just have to understand that shortcoming of the >NUMA architecture and work around it. The up-side is that it is very >hard to scale an SMP box beyond 4 cpus. Intel did it with their FUSION >chipset a couple of years back, but their machine looks like two 4-way >boxes coupled with a kludge, and it doesn't perform very well as memory >is still 4-way interleaved, but with 8 processors demanding data. The >NUMA approach scales better, cost-wise, but there is a performance issue >that must be addressed. Ah, just like networking :) I get it now. Thanks for taking the time to explain it and answer my questions.
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