A simple change [0] (intended to improve prefetching) has decreased performance observed in CSIT instead.
For more details see this [1] Gerrit comment.

While I do not really understand what the Change was aimed to do, and I have no idea how it resulted in more cache misses; I am also unaware of any use case benefiting from [0], so reverting it should be an easy way to restore the performance.

[0] https://gerrit.fd.io/r/c/vpp/+/34568
[1] https://gerrit.fd.io/r/c/vpp/+/34568/2#message-63e1cdafce46e7d389ffb45d79df4fb622681888