We had some reports of slowness on one of our moodle sites. It turned out the school had my moodle redirect switched on.
Upon investigating the performance log I discovered for a single user /my/ page was causing 12401 database queries.
Here is a perf log line from my dev machine (artificially fast due to front/backend being the same).
[Tue Feb 10 19:38:55 2009] [error] [client 10.0.0.5] PERF: /my/ time: 5.407977s memory_total: 21916276B (20.9MB) memory_growth: 21626784B (20.6MB) memory_peak: 22259484B (21.2MB) includecount: 80 dbqueries: 12401 ticks: 541 user: 211 sys: 144 cuser: 0 csys: 0 serverload: 0.11 rcache: 0/0
I want to investigate this and search and destroy whatever is causing it. This obviously cripples a moodle site with my moodle redirection.