Subject: Re: problems with ahc vs. format command
To: Manuel Bouyer <firstname.lastname@example.org>
From: Todd Vierling <email@example.com>
Date: 06/12/2001 12:45:02
On Tue, 12 Jun 2001, Manuel Bouyer wrote:
: > callout_reset(&scb->xs->xs_callout,
: > (newtimeout > 3*1000*1000 ?
: > ((newtimeout / 1000 + 1) * hz) : (newtimeout * hz) / 1000),
: > ahc_timeout, scb);
: The question is whenever the test is really less expansive than the
: 64bit computation. I think on some platforms it may be more expensive.
Only on LP64 platforms, really (sparc64, alpha) -- and those could be
conditionally compiled to use solely 64-bit arithmetic.
The flip side is that a 64-bit "/ 1000" is a *lot* slower than its 32-bit
equivalent on ILP32 platforms, particularly those for which even integer
divide is a library function (sparc v7).
We need to take a harder look at the places where we're gratuitously
increasing integer op overhead in critical paths. Given that disk activity
is a common occurrence, I can see the advantage of using 32-bit arithmetic
-- Todd Vierling <firstname.lastname@example.org> * Wasabi NetBSD: Run with it.
-- NetBSD 1.5 now available on CD-ROM -- http://www.wasabisystems.com/