Want to squeeze a bit more performance out of your MySQL install? Make sure you're not using swap!

Of course you were probably smart enough to make sure MySQL wasn't using all the systems memory to begin with so in theory you shouldn't be swapping. Good idea but the Linux VM isn't that clever.

It can still make poor decisions and decide to swap portions of MySQL out to disk which can end up hindering performance when it needs to page them back into memory. In replicated installs this can yield to periodic situations where certain MySQL slaves fall far behind and take 30 minutes or more to catch up with the master.

If you're not sure your MySQL install isn't using swap you can use vmstat to see realtime stats but I'd recommend using Munin or Ganglia as well.

What you …

Did you know you can change some Linux mount options at runtime? You can and it works just fine.

mount -o noatime,remount,rw /dev/hda3

Will do a live remount and just change the necessary options.

I specifically just did this to add noatime to benchmark the performance update.

You should theoretically be able to do this on a live and production machine but I'd recommend doing this with the machine out of service, all daemons shutdown, and the filesystem sync'd.