Date: Fri, 11 Jan 2002 19:49:04 -0800 From: Peter Wemm <peter@wemm.org> To: Mark Murray <mark@grondar.za> Cc: Chris Faulhaber <jedgar@fxp.org>, scottl@FreeBSD.ORG, smp@FreeBSD.ORG Subject: Re: P5 vs. SMP, part 2 Message-ID: <20020112034904.7784A38FD@overcee.netplex.com.au> In-Reply-To: <200201112015.g0BKFE103071@grimreaper.grondar.org>
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Mark Murray wrote:
> > I wonder how many dual P5's are still being used :/
>
> I have one (2xP5 @200MHz); I use it only in desktop mode, and it
> launches X and Mozilla-CURRENT very slowly. I'm running CURRENT.
The good news is that I found part of the problem. Fix:
Index: machdep.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/i386/machdep.c,v
retrieving revision 1.385.2.21
diff -u -1 -2 -r1.385.2.21 machdep.c
--- machdep.c 2001/12/13 19:18:00 1.385.2.21
+++ machdep.c 2002/01/12 03:35:12
@@ -1093,24 +1093,25 @@
void
cpu_setregs(void)
{
unsigned int cr0;
cr0 = rcr0();
cr0 |= CR0_NE; /* Done by npxinit() */
cr0 |= CR0_MP | CR0_TS; /* Done at every execve() too. */
#ifdef I386_CPU
if (cpu_class != CPUCLASS_386)
#endif
cr0 |= CR0_WP | CR0_AM;
+ cr0 &= ~(CR0_CD | CR0_NW);
load_cr0(cr0);
load_gs(_udatasel);
}
static int
sysctl_machdep_adjkerntz(SYSCTL_HANDLER_ARGS)
{
int error;
error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2,
req);
if (!error && req->newptr)
resettodr();
The problem is that the AP cpus were running with the CR0_CD (cache disable)
and CR0_NW (cache writethrough, not writeback). This is very bad. :-]
PPro and above bioses seem to cause the AP cpus enter the kernel with cache
enabled, so that this looks like it should be a p5/i586 problem only.
Cheers,
-Peter
--
Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au
"All of this is for nothing if we don't go to the stars" - JMS/B5
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