Re: page fault scalability patch V8: [4/7] universally available cmpxchg on i386

Andi Kleen
2004-09-21T15:45:54Z

On Tue, Sep 21, 2004 at 06:41:25PM +0300, Denis Vlasenko wrote:
> On Monday 20 September 2004 23:57, Andi Kleen wrote:
> > On Mon, Sep 20, 2004 at 01:49:20PM -0700, Christoph Lameter wrote:
> > > On Mon, 20 Sep 2004, Denis Vlasenko wrote:
> > >
> > > > I think it shouldn't be this way.
> > > >
> > > > OTOH for !CONFIG_386 case it makes perfect sense to have it inlined.
> > >
> > > Would the following revised patch be acceptable?
> >
> > You would need an EXPORT_SYMBOL at least. But to be honest your
> > original patch was much simpler and nicer and cmpxchg is not called
> > that often that it really matters. I would just ignore Denis'
> > suggestion and stay with the old patch.
>
> A bit faster approach (for CONFIG_386 case) would be using

It's actually slower. Many x86 CPUs cannot predict indirect jumps
and those that do cannot predict them as well as a test and jump.

-Andi