Re: When substitute download + decompression is CPU-bound

[Ludovic Courtès]

Pierre Neidhardt <mail@ambrevar.xyz> skribis:

> On Guillaume's graph, the compression speed at the default level 3 is
> about 110 MB/s, while at level 10 it's about 40 MB/s, which is
> approximately the gzip speed.
>
> If server compression time does not matter, then I agree, level >= 10
> would be a good option.
>
> What about zstd level 19 then?  It's as slow as lzip to compress, but
> decompresses still blazingly fast, which is what we are trying to
> achieve here, _while_ offering a compression ration in the ballpark of
> lzip level 6 (but still not that of lzip level 9).

We could do that.  I suppose a possible agenda would be:

  1. Start providing zstd susbstitutes anytime.  However, most clients
     will keep choosing lzip because it usually compresses better.

  2. After the next release, stop providing lzip substitutes and provide
     only gzip + zstd-19.

This option has the advantage that it wouldn’t break any installation.
It’s not as nice as the ability to choose a download strategy, as we
discussed earlier, but implementing that download strategy sounds
tricky.

Thoughts?

Ludo’.