> On May 4, 2020, at 6:31 PM, Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote: > > Looks like since zstd v1.3.4 there are five negative levels (also > --fast levels), that looks like they'd be in the ballpark of competing > with lz4. That might be useful even with some of the faster NVMe > drives, ~2G/s. > > Any idea if it's possible or even likely? Zstd in the kernel would have to be updated to a newer version for this to be possible. As zstd development slows down, I want to spend some time to update the version in the kernel. But, I don’t expect to find the time to do this for some time. After that there is a limitation in the number of bits required to store the compression Level. Last time I looked there were 15 possible values. These naturally map to compression levels 1-15. That isn’t necessarily set in stone, but the BtrFS folks would could answer that better. Best, Nick
