svn commit: r228248 - stable/8/sys/vm
Alan Cox
alc at FreeBSD.org
Sat Dec 3 23:36:36 UTC 2011
Author: alc
Date: Sat Dec 3 23:36:36 2011
New Revision: 228248
URL: http://svn.freebsd.org/changeset/base/228248
Log:
MFC r215597
Optimize vm_object_terminate().
Modified:
stable/8/sys/vm/vm_object.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
Modified: stable/8/sys/vm/vm_object.c
==============================================================================
--- stable/8/sys/vm/vm_object.c Sat Dec 3 22:16:36 2011 (r228247)
+++ stable/8/sys/vm/vm_object.c Sat Dec 3 23:36:36 2011 (r228248)
@@ -679,7 +679,7 @@ vm_object_destroy(vm_object_t object)
void
vm_object_terminate(vm_object_t object)
{
- vm_page_t p;
+ vm_page_t p, p_next;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
@@ -719,23 +719,41 @@ vm_object_terminate(vm_object_t object)
object->ref_count));
/*
- * Now free any remaining pages. For internal objects, this also
- * removes them from paging queues. Don't free wired pages, just
- * remove them from the object.
+ * Free any remaining pageable pages. This also removes them from the
+ * paging queues. However, don't free wired pages, just remove them
+ * from the object. Rather than incrementally removing each page from
+ * the object, the page and object are reset to any empty state.
*/
vm_page_lock_queues();
- while ((p = TAILQ_FIRST(&object->memq)) != NULL) {
+ TAILQ_FOREACH_SAFE(p, &object->memq, listq, p_next) {
KASSERT(!p->busy && (p->oflags & VPO_BUSY) == 0,
- ("vm_object_terminate: freeing busy page %p "
- "p->busy = %d, p->oflags %x\n", p, p->busy, p->oflags));
+ ("vm_object_terminate: freeing busy page %p", p));
+ /*
+ * Optimize the page's removal from the object by resetting
+ * its "object" field. Specifically, if the page is not
+ * wired, then the effect of this assignment is that
+ * vm_page_free()'s call to vm_page_remove() will return
+ * immediately without modifying the page or the object.
+ */
+ p->object = NULL;
if (p->wire_count == 0) {
vm_page_free(p);
cnt.v_pfree++;
- } else {
- vm_page_remove(p);
}
}
vm_page_unlock_queues();
+ /*
+ * If the object contained any pages, then reset it to an empty state.
+ * None of the object's fields, including "resident_page_count", were
+ * modified by the preceding loop.
+ */
+ if (object->resident_page_count != 0) {
+ object->root = NULL;
+ TAILQ_INIT(&object->memq);
+ object->resident_page_count = 0;
+ if (object->type == OBJT_VNODE)
+ vdrop(object->handle);
+ }
#if VM_NRESERVLEVEL > 0
if (__predict_false(!LIST_EMPTY(&object->rvq)))
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