linux-kernel - Re: [patch 04/17] Add pagetable accessors to pack and unpack pagetable entries

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Date:	Thu, 05 Apr 2007 08:59:09 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Andi Kleen <ak@...e.de>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	virtualization@...ts.osdl.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [patch 04/17] Add pagetable accessors to pack and unpack
	pagetable entries

On Wed, 2007-04-04 at 17:56 +0200, Andi Kleen wrote:
> On Wednesday 04 April 2007 17:45:44 Jeremy Fitzhardinge wrote:
> > Andi Kleen wrote:
> > > Why is there a difference for null syscall? I had assumed we patched all the 
> > > fast path cases relevant there. Do you have an idea where it comes from?
> > 
> > Sure.  There's indirect calls for things like sti/cli/iret.  It goes
> > back to native speed when you patch the real instructions inline.
> 
> I was talking about the patched case. It seemed to be a little slower
> too, but in theory it shouldn't have been, no? 

You'll still have the damage inflicted on gcc's optimizer, though.

Rusty.

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