Comment 336 for bug 620074

I am using Ubuntu 9.04 with 2.6.30-rc3 x86_64 Kernel and I can confirm the whole behavior.
The irony is that it feels like Windows 95 while a floppy was formated. You know, the whole pseudo multi tasking on top of Dos - everything was really choppy.
A easy testcase is to set up two luks encrypted partitions and copy from one to another. Even if no core is under heavy load everything is slow. The same happens with usb transfers too.
But as like Matt Whitlock pointed out it is not always a disk io problem. Even under higher cpu usage this could happen. If I encode a DVD with ogmrip/mencoder h264 and 16 threads (16 threads get the highest cpu usage from my quad core which is still under 80% per core) Gnome feels like a formatting Win 95.
The latest problem has become less severe with 2.6.30-rc3 but it is still noticeable slow which makes no sense since no core has 100% load.
To have an comparison how it could work. If I fire up Prime95 whith 100% load on every core in Windows Vista I can still play modern 3D games without lagging. Windows of course has also flaws with IO and so on but the cpu multi tasking works really great. Way to go imho.