I have noticed this now on my laptop, on JackRabbit, on a few other systems. The Ubuntu kernels are thrashing with context switches. 4000-5000 or so per second, and fast machines are rendered sluggish.
So we build our own. Did that for Ubuntu thus far, and it has been good. Context switches per second down around 100 or so at idle. Where they should be.
I just wonder if anyone at Canonical is paying attention to this. I will file a bug report later on.
As a rule of thumb, if your kernel is thrashing, driving your CPU temperature up when you are idling, you are probably, very likely, doing something horribly wrong. Best guess would be one of their patches hosed the system somehow. This was with both generic and rt kernels.
I used Gutsy beta 1 as the test bed, as I wanted my compiz back. Had it on SuSE, want it on Ubuntu. For reasons I didn’t grasp, it was horribly completely broken in 7.04. It sorta kinda works in 7.10. Takes a little finesse.
This almost makes me want to try SuSE 10.3 on the laptop. With Ubuntu, most everything just works, though on this laptop, the new nVidia chips and the intel wireless driver didn’t in 7.04, nor did the sound. I fixed all of those with updated drivers and a custom kernel build. This kernel is the one which is very well behaved. Loading 7.10 on the system, wiping the old system, and the kernel and system are sluggish. Huge number of context swaps.
On our other systems with Ubuntu, without our kernel, they are sluggish. With our kernel they are peppy.
Someone at Canonical is not building good kernels.