Re: Intel P6 vs P7 system call performance

Daniel Jacobowitz
2002-12-17T20:26:04Z

On Tue, Dec 17, 2002 at 12:06:29PM -0800, Ulrich Drepper wrote:
> Linus Torvalds wrote:
>
> > The thing is, gettimeofday() isn't _that_ special. It's just not worth a
> > vsyscall of it's own, I feel. Where do you stop? Do we do getpid() too?
>
> This is why I'd say mkae no distinction at all. Have the first
> nr_syscalls * 8 bytes starting at 0xfffff000 as a jump table. We can
> transfer to a different slot for each syscall. Each slot then could be
> a PC-relative jump to the common sysenter code or to some special code
> sequence which is also in the global page.
>
> If we don't do this now and it seems desirable in future we wither have
> to introduce a second ABI for the vsyscall stuff (ugly!) or you'll have
> to do the demultiplexing yourself in the code starting at 0xfffff000.

But what does this do to things like PTRACE_SYSCALL? And do we care...
I suppose not if we keep the syscall trace checks on every kernel entry
path.

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer