Sebastian Andrzej Siewior wrote in <20200908195245.gs5ve6fsvbyseuhx@flow>: |On 2020-09-08 15:06:31 [+0200], Steffen Nurpmeso wrote: |> Sebastian Andrzej Siewior wrote in |> <20200908073415.ymmao6fcemn5hqns@flow>: |>|A key stroke is here 10 bytes of raw data which zstd compresses usually |>|into 10 bytes while zlib manages to squeeze it into 5 bytes. This leads |>|to better compression ratio for zlib in ssh's accounting (visible in |>|verbose mode after connection terminates). The data length, that will be |>|transferred over the wire, is the same for 5 and 10 bytes data after the |>|crypto part (with padding and so on). |> |> Then something must be wrong on the configuration side for sure. |> I personally have switched all possible private use cases to zstd |> years ago, in can be configured to be tremendously fast, faster |> even than lz4, no?, or compress almost as good as xz, it depends |> on the data, xz can surely outperform it in size. |> On the decompression side zstd is just tremendously fast. |> And all in one algorithm. | |I don't follow. A key stroke is one ssh packet which has 10 bytes. |This packet must be compressed in a way that it can be fully |decompressed once received on the remote side (ZSTD_e_flush in zstd |terms which finishes the current block). Due to the way framing works in |zstd we end up with a 10 bytes block. Higher compression levels can |achieve 9 bytes but as I stated it does not make sense due to padding of |the compressed data. The zlib framing is smaller here but then zstd |knows exactly how many bytes it will decompress and when the block/frame |ends. | |Do note that this is not simple file compression where you end up with |one frame and blocks created on demand. I see. Thanks for the explanation. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt) _______________________________________________ openssh-unix-dev mailing list openssh-unix-dev@xxxxxxxxxxx https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev
