hgweb: config option to control zlib compression level
Before this patch, the HTTP transport protocol would always zlib
compress certain responses (notably "getbundle" wire protocol commands)
at zlib compression level 6.
zlib can be a massive CPU resource sink for servers. Some server
operators may wish to reduce server-side CPU requirements while
requiring more bandwidth. This is common on corporate intranets, for
example. Others may wish to use more CPU but reduce bandwidth.
This patch introduces a config option to allow server operators
to control the zlib compression level.
On the "mozilla-unified" generaldelta repository, setting this
value to "0" (disable compression) results in server-side CPU
utilization for a `hg clone` going from ~180s to ~124s CPU time on
my i7-6700K. A level of "1" (which increases the transfer size from
~1,074 MB at level 6 to ~1,222 MB) utilizes ~132s CPU time.
Run Mercurial tests with Vagrant:
$ vagrant up
$ vagrant ssh -c ./run-tests.sh