[NEW] io thread performance is significantly worse when clients use pipelining

[SoftlyRaining]

The Problem

I was benchmarking get/set performance between different release versions and realized that io-threads performance is significantly worse when I test with pipelining=4. It seems that prefetching is not as effective when clients pipeline commands for some reason.

Desired Improvement

I think we should investigate why this is the case and improve prefetching with pipelining, since we recommend some amount of pipelining to get the best performance from Valkey.