My experience with it was: with CSR format, SpMV got about 40x speedup compared to a single CPU core on a RTX 3090, with full core utilization. Rough calculation tells me it's equivalent to 80 GFlops, which is far from the full potential of the card. I thought there was someting wrong with cuSPARSE so I went ahead and wrote a SpMV kernel, based on the code in NVIDIA's past reports. It actually performed slightly better. Fair enough, cuSPARSE has to support all kind of workloads so it might be just that in my case, the handwritten kernel worked better. But still, it would never get to the regime of hundreds of GFlops. After reading various literatures on GPU SpMV implementations getting to the same conclusion, I had to concede that I can't squeeze more GFlops out of it.