FWIW, I thought I had the same problem. But using mainstream kernel didn't change anything. My real problem is that most of my big files are downloaded via bittorrent, which ends up fragmenting files *a lot*. See http://trac.transmissionbt.com/ticket/849 in transmission bug tracker for example. I used shake (http://vleu.net/shake/) to defragment my disk, and now everything is fast again. I plan to switch to ext4 to see if the problem goes away for future downloads.
FWIW, I thought I had the same problem. But using mainstream kernel didn't change anything. My real problem is that most of my big files are downloaded via bittorrent, which ends up fragmenting files *a lot*. See http:// trac.transmissi onbt.com/ ticket/ 849 in transmission bug tracker for example. I used shake (http:// vleu.net/ shake/) to defragment my disk, and now everything is fast again. I plan to switch to ext4 to see if the problem goes away for future downloads.