Date: Sat, 17 Nov 2001 14:10:01 -0800 (PST) From: Ian Dowse <iedowse@maths.tcd.ie> To: freebsd-bugs@FreeBSD.org Subject: Re: i386/22441: pmap_growkernel() is not effective at kernel vm limit of 0xffc00000 Message-ID: <200111172210.fAHMA1026284@freefall.freebsd.org>
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The following reply was made to PR i386/22441; it has been noted by GNATS.
From: Ian Dowse <iedowse@maths.tcd.ie>
To: freebsd-gnats-submit@freebsd.org
Cc: David Greenman <dg@root.com>, dillon@freebsd.org,
peter@freebsd.org
Subject: Re: i386/22441: pmap_growkernel() is not effective at kernel vm limit of 0xffc00000
Date: Sat, 17 Nov 2001 22:07:42 +0000
I think the change proposed by this PR corresponds to the following
patch; pmap_growkernel's `addr' argument is one past the last valid
offset, so we don't want to change it if it is already at the start
of a 4M region. The roundup2() macro does the right thing in this
case, whereas the existing code may increase kernel_vm_end 4M too
far, so it can potentially wrap around to 0.
(See the PR for further details, though dispite what it says, I think
only the following rounding should be changed).
Ian
Index: pmap.c
===================================================================
RCS file: /dump/FreeBSD-CVS/src/sys/i386/i386/pmap.c,v
retrieving revision 1.297
diff -u -r1.297 pmap.c
--- pmap.c 17 Nov 2001 01:56:04 -0000 1.297
+++ pmap.c 17 Nov 2001 21:38:25 -0000
@@ -1587,7 +1587,7 @@
nkpt++;
}
}
- addr = (addr + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
+ addr = roundup2(addr, PAGE_SIZE * NPTEPG);
while (kernel_vm_end < addr) {
if (pdir_pde(PTD, kernel_vm_end)) {
kernel_vm_end = (kernel_vm_end + PAGE_SIZE * NPTEPG) & ~(PAGE_SIZE * NPTEPG - 1);
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