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> My gut instinct is the amount of applications that do a lot of processing but only on a small amount of data are in the minority. The opposite seems a lot more common.

I doubt that. The easily way to find out is to disable the L3 cache on your CPU. If your theory is right, the performance drop should be minimal on most applications.

Note: Even with the L3 cache disabled there is still the L1 and L2 caches but those are pretty small.

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I suspect that L3 impacts performance a lot. I dabbled in running a Windows VM with a GPU passthrough, and I had to spend a lot of time to properly pin virtual cores to physical ones so that CPU caches are utilized properly, as I suspected that it was the reason for decreased performance. I managed to get only L1 and L2 to be utilized properly and it somewhat helped, but L3 was still underutilized due to double-scheduling in both Win VM and Linux hypervisor. Even the basic OS shell suffered from lags, not to mention games.

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