Date: Sun, 18 Aug 2002 17:34:37 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Ian Dowse <iedowse@maths.tcd.ie>, Bruce Evans <bde@zeta.org.au>, arch@FreeBSD.ORG Subject: Re: Solving the stack gap issue Message-ID: <Pine.BSF.4.21.0208181733320.42036-100000@InterJet.elischer.org> In-Reply-To: <Pine.BSF.4.21.0208181659440.42036-100000@InterJet.elischer.org>
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duh.....
restate the question..
On Sun, 18 Aug 2002, Julian Elischer wrote:
>
> On Sun, 18 Aug 2002, Matthew Dillon wrote:
> > I would consider this to be more expensive:
> >
> > proc1()
> > {
> > struct thread *td = curthread;
> > ...
> > proc2(td)
> > }
> >
> > proc2(td)
> > {
> > ...
> > }
> >
> > And this to be less expensive:
> >
> > proc1()
> > {
> > proc2();
> > }
> >
> > proc2()
> > {
> > struct thread *td = curthread;
> >
> > ... use td several times ...
> > }
>
> yes but what about:
>
>
> proc1()
> {
> struct thread *td = curthread;
> ...
> someotherfn(td)
> proc2(td)
> }
>
> proc2(td)
> {
> ...
> ... use td several times ...
> }
>
> vs
> proc1()
> {
> struct thread *td = curthread;
> ...
> someotherfn(td)
> proc2(td)
> }
>
> proc2(td)
> {
> ...
> ... use td several times ...
> }
>
> so that proc1 needs td anyhow..
>
> >
> > At least for I386. Ultimately I think this will be generally true on
> > any architecture. If a procedure uses 'curthread' multiple times loading
> > it into a local at the top of the procedure should be a sufficient
> > optimization. Passing td around to dozens or hundreds of procedures
> > just for the sake of avoiding accessing 'curthread' is bad design.
> >
> > -Matt
> > Matthew Dillon
> > <dillon@backplane.com>
> >
>
>
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