Gzip level 1 compression is still too high for many users of import/export

[dralley]

Even the lowest level of gzip compression, level 1, consumes an inordinate and disproportionately high amount of compute time compared to the benefit received from the compression (which is in most cases tiny, since often the data is compressed to begin with)

For example with no compression at all, an export of CentOS Stream 9 BaseOS + RHEL 9 BaseOS required 11.8gb of disk.

With Level 1 compression, it required 11.4gb. With Level 9 compression, it required 11.3gb.

For this result, on my system, 63% of the export time was spent on compressing the exports. Going from level 9 to level 1 to level 0 brought the runtime from 10.5min, to 8.5min, to 4min respectively.

Users of import/export are often dealing with data on the scale of hundreds of gigabytes or multiple terabytes, and disk space seems to be less an issue than the amount of time these exports take. It's best that we default to no compression at all, and look at making it configurable later.

Luckily "gzip level 0" does exist, and packs everything into a gzip archive without performing compression. So we can drop this change in without breaking compatibility with anything.

[pulpbot]

https://bugzilla.redhat.com/show_bug.cgi?id=2239183