Zuul merge operations are quite slow. The reason is that fetches from Gerrit are painfully slow for some repositories:
Under zuul@gallium:/srv/ssd/zuul/git/ :
mediawiki/core$ time git fetch --dry-run real 0m18.353s user 0m17.781s sys 0m0.236s
The operation is quite long because git send all references to the remote. And:
$ git show-ref|fgrep -c refs/zuul 51185 $
We need a script that list all references matching refs/zuul/* , inspect the commit date and delete the reference it is older than X days (for example 30 days). That will help git fetch operation and thus speed up Zuul merge operations.
to run the job until it is puppetized/packaged
find /srv/ssd/zuul/git/ -name .git -type d -print -exec /home/hashar/zuul-clear-refs.py --until 30 {} \;