Date: Thu, 31 Jan 2002 18:17:47 -0800 From: Peter Wemm <peter@wemm.org> To: Terry Lambert <tlambert2@mindspring.com> Cc: "Cameron, Frank" <Cameron@ctc.com>, "'Kenneth Culver'" <culverk@yumyumyum.org>, David Malone <dwmalone@maths.tcd.ie>, "'freebsd-bugs@freebsd.org'" <freebsd-bugs@FreeBSD.ORG>, "'freebsd-current@freebsd.org'" <freebsd-current@FreeBSD.ORG> Subject: Re: AMD AGP Bug Message-ID: <20020201021747.A50863809@overcee.wemm.org> In-Reply-To: <3C59E050.6564C115@mindspring.com>
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Terry Lambert wrote:
> "Cameron, Frank" wrote:
> > From what was posted on the linux-kernel list the problem is the OS
> > doing the wrong thing not the hardware. I originally asked the
> > question (albeit not worded as clearly as I should have) because if
> > Microsoft and Linux programmers made the same mistake, might
> > FreeBSD have also.
>
> No. FreeBSD does not make active use of 4M pages for anything
> other than the initial kernel text and data, which is obvious,
> if you look at /sys/i386/machdep.c.
Actually, it is obvious if you actually do look at the pmap.c that we *do*
use 4MB pages for device mappings.
/*
* This code maps large physical mmap regions into the
* processor address space. Note that some shortcuts
* are taken, but the code works.
*/
if (pseflag && (object->type == OBJT_DEVICE) &&
((addr & (NBPDR - 1)) == 0) && ((size & (NBPDR - 1)) == 0)) {
...
for(i = 0; i < npdes; i++) {
pmap->pm_pdir[ptepindex] =
ptepa | PG_U | PG_RW | PG_V | PG_PS;
ptepa += NBPDR;
ptepindex += 1;
}
...
Even doing a simple grep for the 4MB page flag (PG_PS) and using a
little initiative would have shown this.
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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