adding discard options to ext4 on SSD is not a good idea.
when removing a lot of small files (make clean ?), it can freeze a computer for 5-10min.
it's the case on my laptop (quad-core with 6G RAM), and a better method is to add fstrim to a crontab.
If you had read the Google+ post, you would know that they actually do this. The are aware of the fact that kernel managed trim has issues.