Some queries slower in MySQL 5.5 than 5.0? We have an exceptionally inefficient process (1.3 million selects, 232k updates) that I'm now recoding to be 1 select and 50 updates. In the meantime, though, today's process ran.

We recently updated one of our slaves to MySQL 5.5, from MySQL 5.0, as a test run before we do it on our master. We're still running everything in MyISAM because we needed it up and running before attempting to do InnoDB optimization. The thing seems to be working fast enough, except for this process. The other slave, with identical hardware, finished it virtually in real time; this slave, however, is running over 2 hours behind because of it.

I'm curious, does anyone know if this type of thing (tons of tiny, simple updates) is slower in MySQL 5.5 for MyISAM in general? The settings between the two servers are as close as settings between a 5.0 and 5.5 can be, so it doesn't necessarily appear to be configuration. So while I can fix it by not having the horrible process, I'm worried that this is indicative of a deeper problem with our server. Should I be, or is it all kosher?

Edit: The problem appears to only be with large numbers of small queries. I just ran one and it was in the "query end" state for .133 seconds, or 89% of the query time. Only being able to run ten queries per second on a single thread seems pretty bad. Does 5.5 change things such that I need to modify my cnf file?
Disabling the binary log on the slave fixed it. This makes me worry about when we upgrade the master to 5.5, but for now things are working much much better.

Edit: The issue was sync_binlog; now that it's set to zero, everything's happy.