Techgage posted a guide on enabling TRIM under Linux, and also checking to make sure it works as intended.

Owning an SSD that supports TRIM is great, but while Windows users have the benefit of having TRIM enabled for them, Linux users need to take the manual route - at least, at this point in time. In this article, we tackle the simple process of doing so, and also show how to verify that TRIM is indeed working as it should be.

  Enabling and Testing SSD TRIM Support Under Linux