svn commit: r236930 - head/sys/amd64/amd64

[Alan Cox]

Author: alc
Date: Mon Jun 11 21:41:16 2012
New Revision: 236930
URL: http://svn.freebsd.org/changeset/base/236930

Log:
  Avoid unnecessary atomic operations for clearing PGA_WRITEABLE in
  pmap_remove_pages().  This reduces pmap_remove_pages()'s running time by
  4 to 11% in my tests.
  
  MFC after:	1 week

Modified:
  head/sys/amd64/amd64/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Mon Jun 11 21:40:02 2012	(r236929)
+++ head/sys/amd64/amd64/pmap.c	Mon Jun 11 21:41:16 2012	(r236930)
@@ -4197,7 +4197,8 @@ pmap_remove_pages(pmap_t pmap)
 					TAILQ_REMOVE(&pvh->pv_list, pv, pv_list);
 					if (TAILQ_EMPTY(&pvh->pv_list)) {
 						for (mt = m; mt < &m[NBPDR / PAGE_SIZE]; mt++)
-							if (TAILQ_EMPTY(&mt->md.pv_list))
+							if ((mt->aflags & PGA_WRITEABLE) != 0 &&
+							    TAILQ_EMPTY(&mt->md.pv_list))
 								vm_page_aflag_clear(mt, PGA_WRITEABLE);
 					}
 					mpte = pmap_lookup_pt_page(pmap, pv->pv_va);
@@ -4213,7 +4214,8 @@ pmap_remove_pages(pmap_t pmap)
 				} else {
 					pmap_resident_count_dec(pmap, 1);
 					TAILQ_REMOVE(&m->md.pv_list, pv, pv_list);
-					if (TAILQ_EMPTY(&m->md.pv_list) &&
+					if ((m->aflags & PGA_WRITEABLE) != 0 &&
+					    TAILQ_EMPTY(&m->md.pv_list) &&
 					    (m->flags & PG_FICTITIOUS) == 0) {
 						pvh = pa_to_pvh(VM_PAGE_TO_PHYS(m));
 						if (TAILQ_EMPTY(&pvh->pv_list))