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Date:      Sun, 29 Jul 2012 18:20:50 +0000 (UTC)
From:      Alan Cox <alc@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r238889 - head/sys/amd64/amd64
Message-ID:  <201207291820.q6TIKoig082493@svn.freebsd.org>
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Author: alc
Date: Sun Jul 29 18:20:49 2012
New Revision: 238889
URL: http://svn.freebsd.org/changeset/base/238889

Log:
  Shave off a few more cycles from pmap_enter()'s critical section.  In
  particular, do a little less work with the PV list lock held.

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

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Sun Jul 29 18:04:38 2012	(r238888)
+++ head/sys/amd64/amd64/pmap.c	Sun Jul 29 18:20:49 2012	(r238889)
@@ -3446,6 +3446,7 @@ pmap_enter(pmap_t pmap, vm_offset_t va, 
 	KASSERT(va < UPT_MIN_ADDRESS || va >= UPT_MAX_ADDRESS,
 	    ("pmap_enter: invalid to pmap_enter page table pages (va: 0x%lx)",
 	    va));
+	KASSERT((prot & access) == access, ("pmap_enter: access not in prot"));
 	KASSERT((m->oflags & VPO_UNMANAGED) != 0 || va < kmi.clean_sva ||
 	    va >= kmi.clean_eva,
 	    ("pmap_enter: managed mapping within the clean submap"));
@@ -3453,7 +3454,9 @@ pmap_enter(pmap_t pmap, vm_offset_t va, 
 	    VM_OBJECT_LOCKED(m->object),
 	    ("pmap_enter: page %p is not busy", m));
 	pa = VM_PAGE_TO_PHYS(m);
-	newpte = (pt_entry_t)(pa | pmap_cache_bits(m->md.pat_mode, 0) | PG_V);
+	newpte = (pt_entry_t)(pa | PG_A | PG_V);
+	if ((access & VM_PROT_WRITE) != 0)
+		newpte |= PG_M;
 	if ((prot & VM_PROT_WRITE) != 0)
 		newpte |= PG_RW;
 	if ((prot & VM_PROT_EXECUTE) == 0)
@@ -3464,6 +3467,7 @@ pmap_enter(pmap_t pmap, vm_offset_t va, 
 		newpte |= PG_U;
 	if (pmap == kernel_pmap)
 		newpte |= PG_G;
+	newpte |= pmap_cache_bits(m->md.pat_mode, 0);
 
 	mpte = om = NULL;
 
@@ -3495,7 +3499,6 @@ retry:
 		panic("pmap_enter: invalid page directory va=%#lx", va);
 
 	origpte = *pte;
-	opa = origpte & PG_FRAME;
 
 	/*
 	 * Is the specified virtual address already mapped?
@@ -3507,9 +3510,9 @@ retry:
 		 * are valid mappings in them. Hence, if a user page is wired,
 		 * the PT page will be also.
 		 */
-		if (wired && (origpte & PG_W) == 0)
+		if ((newpte & PG_W) != 0 && (origpte & PG_W) == 0)
 			pmap->pm_stats.wired_count++;
-		else if (!wired && (origpte & PG_W))
+		else if ((newpte & PG_W) == 0 && (origpte & PG_W) != 0)
 			pmap->pm_stats.wired_count--;
 
 		/*
@@ -3523,17 +3526,20 @@ retry:
 		}
 
 		/*
-		 * Has the mapping changed?
+		 * Has the physical page changed?
 		 */
+		opa = origpte & PG_FRAME;
 		if (opa == pa) {
 			/*
 			 * No, might be a protection or wiring change.
 			 */
 			if ((origpte & PG_MANAGED) != 0) {
 				newpte |= PG_MANAGED;
+				if ((newpte & PG_RW) != 0)
+					vm_page_aflag_set(m, PGA_WRITEABLE);
 				om = m;
 			}
-			if ((origpte & ~(PG_M | PG_A)) == newpte)
+			if (((origpte ^ newpte) & ~(PG_M | PG_A)) == 0)
 				goto unchanged;
 			goto validate;
 		} else {
@@ -3547,7 +3553,7 @@ retry:
 		/*
 		 * Increment the counters.
 		 */
-		if (wired)
+		if ((newpte & PG_W) != 0)
 			pmap->pm_stats.wired_count++;
 		pmap_resident_count_inc(pmap, 1);
 	}
@@ -3561,21 +3567,18 @@ retry:
 		pv->pv_va = va;
 		CHANGE_PV_LIST_LOCK_TO_PHYS(&lock, pa);
 		TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
+		if ((newpte & PG_RW) != 0)
+			vm_page_aflag_set(m, PGA_WRITEABLE);
 	}
 
-validate:
-
 	/*
 	 * Update the PTE.
 	 */
-	newpte |= PG_A;
-	if ((access & VM_PROT_WRITE) != 0)
-		newpte |= PG_M;
-	if ((newpte & (PG_MANAGED | PG_RW)) == (PG_MANAGED | PG_RW))
-		vm_page_aflag_set(m, PGA_WRITEABLE);
 	if ((origpte & PG_V) != 0) {
+validate:
 		invlva = FALSE;
 		origpte = pte_load_store(pte, newpte);
+		opa = origpte & PG_FRAME;
 		if ((origpte & PG_A) != 0 && (opa != pa ||
 		    ((origpte & PG_NX) == 0 && (newpte & PG_NX) != 0)))
 			invlva = TRUE;

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