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2 docs tagged with "latency"

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Latency, Throughput, and Latency Hiding

Latency and throughput sound like the same idea measured two ways, but a GPU treats them as almost unrelated design targets. Latency is how long one memory request takes to come back; throughput is how many bytes per second the memory system can sustain in steady state. A single DRAM access on a modern GPU takes several hundred nanoseconds — not meaningfully faster than it was a decade ago — yet the same hardware sustains terabytes per second in aggregate. The only way to reconcile a slow individual request with a fast aggregate rate is to have an enormous number of requests outstanding at once, and that single fact is why the CUDA programming model insists you expose thousands of threads instead of a handful.