"use register arguments" option enabled.

Ignacio Vazquez-Abrams ivazquez at ivazquez.net
Mon May 16 23:01:59 UTC 2005


On Tue, 2005-05-17 at 10:45 +1200, Mike Honeyfield wrote:
> On 5/17/05, Ignacio Vazquez-Abrams <ivazquez at ivazquez.net> wrote:
> > On Tue, 2005-05-17 at 10:29 +1200, Mike Honeyfield wrote:
> > > I am just wondering the reasoning behind having the experimental
> > > option "Use register arguments" on in the kernel config.
> > >
> > > It has caused some issues for me, have since fixed it, but was
> > > wondering why an experimental feature that could/can break the ABI for
> > > 3rd party binary only modules would be enabled?
> > 
> > Speed. Pushing data onto the stack takes longer than just shoving it
> > into a register.
> > 
> 
> So the speed improvement is enough to justify this? 

Even a 2 clock cycle delay happening hundreds of thousands or even
millions of times a second builds up.

> I could understand Fedora Core's kernels have this feature, but was a
> bit suprised to see the same issue in RHEL.

Agreed. But then again it really shouldn't affect a large number of
modules.

-- 
Ignacio Vazquez-Abrams <ivazquez at ivazquez.net>
http://fedora.ivazquez.net/

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