Since Linux 5.5, three additional checksum algorithms have been supported by btrfs. These are XXHASH, SHA256 and BLAKE2b. The "all" make target does not cover the hash-speedtest utility. I think that it would be useful if the ebuild were to install it. In particular, XXHASH is an interesting alternative to CRC32C and I was mildly surprised to find that it outperforms CRC32C on my hardware.
Created attachment 840903 [details, diff] 0001-sys-fs-btrfs-progs-Also-install-hash-speedtest.patch I'm not sure that this is the best way of going about it but it worked for me.
On second thoughts, I'm retracting this request. The hash-speedtest utility doesn't make use of the kernel crypto API, so one cannot necessarily assume that the benchmark results are indicative of the performance that can be expected.
