Last time I went away a couple of weeks ago I left my MacBook at home and when I got back it seemed to not be working as it did previously.

I have had a look at some "speed up my Mac" type pages on the web, cleared caches, downloaded OnyX and run it, cleared surplus icons off the desktop, repaired disk permissions and it still isn't running as it did before I went away.

According to activity monitor, my CPU usage is less than 10% and I have half my memory free.

kernel_task is swallowing a lot of memory, tabs in browsers seem to be consuming a lot too, and if I import a week's worth of photos into Lightroom then that swallows up a GB too.

None of my usage has changed but before I went away I could chirpily have MS Word, MS Excel, Lightroom, Illustrator and Photoshop all open at the same time as well as 6 or 7 tabs open in each of Chrome and Firefox. Now I cannot do half of that without hanging and getting the beach ball.

The only software that updated itself before I went away was Firefox, but using Safari instead doesn't seem to have solved the problem.

Anyone got any tips or am I resigned to buying more memory? I have 4GB but like I said it was plenty before I went away for a couple of days 2 weeks ago