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Date:      Sun, 24 Sep 2017 16:50:10 +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: r323973 - head/sys/vm
Message-ID:  <201709241650.v8OGoADH032431@repo.freebsd.org>
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Author: alc
Date: Sun Sep 24 16:50:10 2017
New Revision: 323973
URL: https://svnweb.freebsd.org/changeset/base/323973

Log:
  Optimize vm_page_try_to_free().  Specifically, the call to pmap_remove_all()
  can be avoided when the page's containing object has a reference count of
  zero.  (If the object has a reference count of zero, then none of its pages
  can possibly be mapped.)
  
  Address nearby style issues in vm_page_try_to_free(), and change its
  return type to "bool".
  
  Reviewed by:	kib, markj
  MFC after:	1 week

Modified:
  head/sys/vm/vm_page.c
  head/sys/vm/vm_page.h

Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c	Sun Sep 24 14:36:01 2017	(r323972)
+++ head/sys/vm/vm_page.c	Sun Sep 24 16:50:10 2017	(r323973)
@@ -3081,23 +3081,25 @@ vm_page_unswappable(vm_page_t m)
  * vm_page_try_to_free()
  *
  *	Attempt to free the page.  If we cannot free it, we do nothing.
- *	1 is returned on success, 0 on failure.
+ *	true is returned on success, false on failure.
  */
-int
+bool
 vm_page_try_to_free(vm_page_t m)
 {
 
-	vm_page_lock_assert(m, MA_OWNED);
+	vm_page_assert_locked(m);
 	if (m->object != NULL)
 		VM_OBJECT_ASSERT_WLOCKED(m->object);
-	if (m->dirty || m->hold_count || m->wire_count ||
+	if (m->dirty != 0 || m->hold_count != 0 || m->wire_count != 0 ||
 	    (m->oflags & VPO_UNMANAGED) != 0 || vm_page_busied(m))
-		return (0);
-	pmap_remove_all(m);
-	if (m->dirty)
-		return (0);
+		return (false);
+	if (m->object != NULL && m->object->ref_count != 0) {
+		pmap_remove_all(m);
+		if (m->dirty != 0)
+			return (false);
+	}
 	vm_page_free(m);
-	return (1);
+	return (true);
 }
 
 /*

Modified: head/sys/vm/vm_page.h
==============================================================================
--- head/sys/vm/vm_page.h	Sun Sep 24 14:36:01 2017	(r323972)
+++ head/sys/vm/vm_page.h	Sun Sep 24 16:50:10 2017	(r323973)
@@ -477,7 +477,6 @@ void vm_page_change_lock(vm_page_t m, struct mtx **mtx
 vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
 int vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
     vm_page_t *ma, int count);
-int vm_page_try_to_free (vm_page_t);
 void vm_page_deactivate (vm_page_t);
 void vm_page_deactivate_noreuse(vm_page_t);
 void vm_page_dequeue(vm_page_t m);
@@ -513,6 +512,7 @@ void vm_page_set_valid_range(vm_page_t m, int base, in
 int vm_page_sleep_if_busy(vm_page_t m, const char *msg);
 vm_offset_t vm_page_startup(vm_offset_t vaddr);
 void vm_page_sunbusy(vm_page_t m);
+bool vm_page_try_to_free(vm_page_t m);
 int vm_page_trysbusy(vm_page_t m);
 void vm_page_unhold_pages(vm_page_t *ma, int count);
 void vm_page_unswappable(vm_page_t m);

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