Comment 3 for bug 1881089

zlib indeed made sbcl startup unacceptably slow for my use case, and switching to lz4 made it fast enough. This was discussed in the "Interest in patch incorporating lz4?
" thread: https://sourceforge.net/p/sbcl/mailman/message/32989588/ and the patch is still available (although not updated) in https://github.com/orivej/sbcl/commit/lz4-squashed . I have not tested zstd at the time, but if sbcl was to add one new algorithm now, zstd probably suits it better.