Messages in this thread | | | Date | Sat, 25 Oct 2014 14:59:24 +0800 | From | Daniel J Blueman <> | Subject | RCU fanout leaf balancing |
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Hi Paul,
Finding earlier reference to increasing RCU fanout leaf for the purpose of "decrease[ing] cache-miss overhead for large systems", would your suggestion be to increase the value to the next hierarchy core-count above 16?
If we have say 32 interconnected 48-core servers; 3 sockets of dual-node 8-core Opteron 6300s, so 1536 cores in all. Latency across the coherent interconnect is O(100x) higher than the internal Hypertransport interconnect, so if we set RCU_FANOUT_LEAF to 48 to keep leaf-checking local to one Hypertransport fabric, what wisdom would one use for RCU_FANOUT? 4x leaf?
Or, would it be more cache-friendly to set RCU_FANOUT_LEAF to 8 and RCU_FANOUT to 48?
Many thanks, Daniel -- Daniel J Blueman Principal Software Engineer, Numascale
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