From 052e18485d19f26d4182a662054369926d0c4dd0 Mon Sep 17 00:00:00 2001
From: Austin Clements <amdragon@mit.edu>
Date: Thu, 1 Sep 2011 21:29:09 -0400
Subject: [PATCH] Skip missing page directories in deallocuvm
Previously, deallocuvm scanned from 0 to KERNBASE in one page
increments, which had a noticable effect on boot time. Now it skips
over missing page directories.
---
vm.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/vm.c b/vm.c
index c717baf..181b376 100644
--- a/vm.c
+++ b/vm.c
@@ -261,7 +261,9 @@ deallocuvm(pde_t *pgdir, uint oldsz, uint newsz)
a = PGROUNDUP(newsz);
for(; a < oldsz; a += PGSIZE){
pte = walkpgdir(pgdir, (char*)a, 0);
- if(pte && (*pte & PTE_P) != 0){
+ if(!pte)
+ a += (NPTENTRIES - 1) * PGSIZE;
+ else if((*pte & PTE_P) != 0){
pa = PTE_ADDR(*pte);
if(pa == 0)
panic("kfree");
--
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