Gentoo Linux users typically compile their own kernels, so they do not use those parameters I posted, but as long as you have CONFIG_MTRR_SANITIZER in your kernel .config, you can use those parameters to enable it.
By the way, MTRR has nothing to do with your graphics card. It is an x86 feature. All x86 processors support it.
Over here with KDE 4.5.5, an HD4200 and latest fglrx I get a max of 27% cpu usage on dolphin (that's 27% of one core) when doing the mouse up and down on the places panel. When resizing it goes up to about 45% max.
Maybe you should open a bug at bugs.kde.org and post a link to it here.
I can't believe, that devs aren't aware about this. UDisks integration is extremely buggy. And it's not only about performance.
For example, using optical drive will drive you crazy. Every mouseover, resizing, unminimizing or even window focus will spin-up disk. Not to mention ejecting.
Originally Posted by devius
Over here with KDE 4.5.5, an HD4200 and latest fglrx I get a max of 27% cpu usage on dolphin[...]
So, it's about 26% too much, but really, it's not about KDE SC < 4.6. It's about regressions.