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Usama Arif found that with the three patches to just probe BMI2 CPU support only once, it yield a 71% reduction in decompression time and a 18% reduction in compression time for a crypto_acomp benchmark.
Wow
Is it that slow outside of a VM? Either way, this seems like a very sensible patch.
It’s only slightly faster.
cpuidis a serialising instruction, which means all the instructions before it have to complete, removing any gains from pipelining and out of order execution. However for a VM this also triggers a VM exit, where the hypervisor takes over to modify the values for the guest.