Subject: Re: indirect calls [Re: issues with com and non-PCI platforms.... a proposal]
To: Garrett D'Amore <firstname.lastname@example.org>
From: Pavel Cahyna <email@example.com>
Date: 03/14/2006 22:35:32
On Tue, Mar 14, 2006 at 12:57:01PM -0800, Garrett D'Amore wrote:
> Pavel Cahyna wrote:
> > On Wed, Mar 08, 2006 at 04:30:35PM -0800, Matt Thomas wrote:
> >> On Mar 8, 2006, at 3:59 PM, Garrett D'Amore wrote:
> >>> How does an indirect function call compare against say the cost of
> >>> another array index lookup and an extra shift/mask operation>
> >> for vax, about an order of magnitude.
> > What can be so slow? An indirect function call, or function calls in
> > general? And which architectures especially suffer from expensive indirect
> > function calls?
> My understanding, from what others have said, is that the problem is
> that function calls *in general* are expensive on a VAX.
> It is mind boggling to me, that we have to design our software to
> eliminate function calls where-ever possible, in order to get good
I do not see where this particular problem is - does VAXen use the com
driver at all? From a quick look at files.vax, intro(4) and GENERIC, it
does not seem so.