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From: Alan Cox <alc@FreeBSD.org>
Date: Sat, 10 May 2014 19:47:01 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r265850 - head/sys/vm
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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,