Re: Intel P6 vs P7 system call performance

[Ulrich Drepper]

Linus Torvalds wrote:

> No, the way sysenter works, the table approach just sucks up dcache space
> (the kernel cannot know which sysenter is the one that the user uses
> anyway, so the jump table would have to just add back some index and we'd
> be back exactly where we started)
> 
> I'll keep it the way it is now.

I won't argue since honestly, not doing it is much easier for me.  But I
want to be sure I'm clear.

What I suggested is to have the first part of the global page be

   .p2align 3
   jmp sysenter_label
   .p2align 3
   jmp sysenter_label
   ...
   .p2align
   jmp userlevel_gettimeofday

sysenter_label:
  the usual sysenter code

userlevel_gettimeofday:
  whatever necessary

All this would be in the global page.  There is only one sysenter call.

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