Comment 0 for bug 851213

See the incident report at:

https://wiki.canonical.com/IncidentReports/2011-09-15-LP-Slow%20merge%20proposal%20jobs

While we've determined there wasn't a true incident, we do seem to get merge proposal diff generation taking a while due to a backlog. We're not sure what is causing the backlog, and this bug report is meant to track the issue.