#2749 introduced a noticeable regression in compression ratio of --fast=2 and higher fast compression values for silesia.tar

$ git checkout 80bc12b33a
build
$ ./zstd --fast=3 ~/data/silesia.tar
57.05%   (   267 MiB =>    152 MiB)
$ git checkout ab8aa49b
build
$ ./zstd --fast=3 ~/data/silesia.tar
61.30%   (   267 MiB =>    164 MiB)

164/152 ~ 1.08

Yes, it came with around ~10% CPU performance increase but just to note that I don't see any benchmarks of lower than -1 values in the pull request. And -1 is just fine

At Google we see up to 20% regressions on some data with --fast=3, so I wonder if that's expected