Some tips for speeding up mock via its configuration,
/etc/mock/site-defaults.cfg:

* Disable the package state plugin:
  config_opts['plugin_conf']['package_state_enable'] = False

* Parallelize builds:
  config_opts['macros']['%_smp_mflags'] = "-j17"

* Improve ccache hits between package version builds (may break -debuginfos!):
  config_opts['files']['etc/profile.d/zz-local.sh'] = """
  unset CCACHE_HASHDIR
  """

* Compress ccache:
  config_opts['plugin_conf']['ccache_opts']['compress'] = True

* Use lzo compression for root cache:
  config_opts['plugin_conf']['root_cache_opts']['compress_program'] = "lzop"
  config_opts['plugin_conf']['root_cache_opts']['extension'] = ".lzo"

* Parallelize compression within rpmbuild (in per-repo config files):
  config_opts['chroot_setup_cmd'] = 'install @buildsys-build pigz lbzip2'
  config_opts['macros']['%__gzip'] = '/usr/bin/pigz'
  config_opts['macros']['%__bzip2'] = '/usr/bin/lbzip2'