Author: alc
Date: Sat May 10 19:47:00 2014
New Revision: 265850
URL: http://svnweb.freebsd.org/changeset/base/265850
Log:
About 9% of the pmap_protect() calls being performed by vm_map_copy_entry()
are unnecessary. Eliminate the unnecessary calls.
Reviewed by: kib
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
Modified:
head/sys/vm/vm_map.c
Modified: head/sys/vm/vm_map.c
==============================================================================
--- head/sys/vm/vm_map.c Sat May 10 19:18:49 2014 (r265849)
+++ head/sys/vm/vm_map.c Sat May 10 19:47:00 2014 (r265850)
@@ -3023,7 +3023,8 @@ vm_map_copy_entry(
* If the source entry is marked needs_copy, it is already
* write-protected.
*/
- if ((src_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
+ if ((src_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0 &&
+ (src_entry->protection & VM_PROT_WRITE) != 0) {
pmap_protect(src_map->pmap,
src_entry->start,
src_entry->end,
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