Re: Intel P6 vs P7 system call performance

Benjamin LaHaise
2002-12-17T21:27:00Z

On Tue, Dec 17, 2002 at 10:49:31AM -0800, Linus Torvalds wrote:
> There is only a "call relative" or "call indirect-absolute". So you either
> have to indirect through memory or a register, or you have to fix up the
> call at link-time.
>
> Yeah, I know it sounds strange, but it makes sense. Absolute calls are
> actually very unusual, and using relative calls is _usually_ the right
> thing to do. It's only in cases like this that we really want to call a
> specific address.

The stubs I used for the vsyscall bits just did an absolute jump to
the vsyscall page, which would then do a ret to the original calling
userspace code (since that provided library symbols for the user to
bind against).

-ben
--
"Do you seek knowledge in time travel?"