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SMT also allows the cores to hide memory latency by executing the other thread(s). Taken to the extreme end this would give you a barrel CPU.
by crest 2y ago
SMT also allows the cores to hide memory latency by executing the other thread(s). Taken to the extreme end this would give you a barrel CPU.
- fulafel 2y agoYes, this is reflected in the execution speed of the workloads (vs being an additional thing). Other things making up the potential for being more than a zero sum game (half the speed) include making better use of the ALU and branch units that would otherwise be waiting for dependencies. On the other side of the scale is how different working sets of the threads can thrash each others cache working sets.
- nullc 2y agoI think unfortunately with just 2-way smt it's pretty easy to get both of them stalled at once. The power9 4-way SMT seems to be a fair bit more effective than what I've seen on x86.
- JonChesterfield 2y agoPush the hyperthread count up higher and you have enough stuff to do while waiting on memory that branch prediction doesn't matter as much. Could call it a GPU.