I found something very interesting. I have a Linksys e2000 router and 7 devices (2 wired and 5 wireless) are connected to that router.
I downloaded something with a wireless computer with uTorrent. I found after uTorrents ran for few minutes, my router CPU ran to 80% usage, and this wireless computer got no ping responsse or very slow ping replies. However, at the same time, I tried a different computer (wired or wireless) I got pings and I could visit any websites without any problems.
What should I do to make sure Qos is working correctly, so when P2P actives occurred, the computer still take it and lower its own P2P traffic too for that computer.