Re: zlib-ng as a compat replacement for zlib

[Florian Weimer]

* Richard W. M. Jones:

> I tested the speed of decompression using:
>
>   $ hyperfine 'qemu-img convert -W -m 16 -f qcow2 test.qcow2.XXX -O raw 
> test.out'
>   (qemu 8.0.0-4.fc39.x86_64)
>
>   $ hyperfine 'nbdkit -U - --filter=qcow2dec file test.qcow2.XXX --run 
> '\''nbdcopy --request-size "$uri" test.out'\'' '
>   (nbdkit-1.35.11-2.fc40.x86_64)

How realistic is that?  Larger cluster sizes will make random access
perform noticeably worse is some cases.  Think about reading a few bytes
towards the end of the cluster.  It makes a difference whether you have
to decompress 64 KiB bytes for that, or 2 MiB.  As far as I understand
it, the above commands use all data decompressed, so they don't suffer
from this issue (particularly with read-ahead to deal with unfortunate
cluster boundaries).

Time to first HTTP request served after boot or something like that
might be a better comparison.

Thanks,
Florian