Re: [Bug 350] New: i386 context switch very slow compared to 2.4 due to wrmsr (performance)

Linus Torvalds
2003-03-10T22:35:41Z

On Sun, 9 Mar 2003, Linus Torvalds wrote:
>
> Your SYSENTER_ESP hack would probably get back the rest, but I haven't
> seen any patches for it, hint hint.

Oh, well, I just did it myself. And tested with both NMI's and debug
traps, just to make sure that we do the right thing there too.

(If we get an NMI on the first three instructions in a debug trap that
happens on the first instruction of the sysenter path, we're still
screwed. I'm still trying to figure out a good way to unscrew us).

> In the meantime, we're almost back to where we were _and_ we support
> sysenter (ie my system calls are down by almost a factor of four). So
> we're doing pretty well.

We're now pretty much back to 2.4.x performance on the scheduler, as far
as I can tell. Can people confirm and close the bug?

Linus