Using activity monitor, I've noticed that launchd with pid 1 is using a lot of disk writes: after about 8 hours of light use, it's done ~2GB bytes written. Is it normal behavior? If not, how shall I troubleshoot this issue? I'm on the latest version if Yosemite, MacBook Pro 13" retina. Thanks!
Don't fix things which ain't broken. As long as you don't experience performance or stability issues, you usually don't need to worry about particular processes.
My Mac hasn't been rebooted since two weeks,
launchd has written 46 GB so far.