Author: alc
Date: Tue Oct 25 16:35:08 2011
New Revision: 226740
URL: http://svn.freebsd.org/changeset/base/226740
Log:
Speed up vm_page_cache() and vm_page_remove() by checking for a few
common cases that can be handled in constant time. The insight being
that a page's parent in the vm object's tree is very often its
predecessor or successor in the vm object's ordered memq.
Tested by: jhb
MFC after: 10 days
Modified:
head/sys/vm/vm_page.c
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Tue Oct 25 16:30:16 2011 (r226739)
+++ head/sys/vm/vm_page.c Tue Oct 25 16:35:08 2011 (r226740)
@@ -908,7 +908,7 @@ void
vm_page_remove(vm_page_t m)
{
vm_object_t object;
- vm_page_t root;
+ vm_page_t next, prev, root;
if ((m->oflags & VPO_UNMANAGED) == 0)
vm_page_lock_assert(m, MA_OWNED);
@@ -923,15 +923,42 @@ vm_page_remove(vm_page_t m)
/*
* Now remove from the object's list of backed pages.
*/
- if (m != object->root)
- vm_page_splay(m->pindex, object->root);
- if (m->left == NULL)
- root = m->right;
- else {
- root = vm_page_splay(m->pindex, m->left);
- root->right = m->right;
+ if ((next = TAILQ_NEXT(m, listq)) != NULL && next->left == m) {
+ /*
+ * Since the page's successor in the list is also its parent
+ * in the tree, its right subtree must be empty.
+ */
+ next->left = m->left;
+ KASSERT(m->right == NULL,
+ ("vm_page_remove: page %p has right child", m));
+ } else if ((prev = TAILQ_PREV(m, pglist, listq)) != NULL &&
+ prev->right == m) {
+ /*
+ * Since the page's predecessor in the list is also its parent
+ * in the tree, its left subtree must be empty.
+ */
+ KASSERT(m->left == NULL,
+ ("vm_page_remove: page %p has left child", m));
+ prev->right = m->right;
+ } else {
+ if (m != object->root)
+ vm_page_splay(m->pindex, object->root);
+ if (m->left == NULL)
+ root = m->right;
+ else if (m->right == NULL)
+ root = m->left;
+ else {
+ /*
+ * Move the page's successor to the root, because
+ * pages are usually removed in ascending order.
+ */
+ if (m->right != next)
+ vm_page_splay(m->pindex, m->right);
+ next->left = m->left;
+ root = next;
+ }
+ object->root = root;
}
- object->root = root;
TAILQ_REMOVE(&object->memq, m, listq);
/*
@@ -2021,7 +2048,7 @@ void
vm_page_cache(vm_page_t m)
{
vm_object_t object;
- vm_page_t root;
+ vm_page_t next, prev, root;
vm_page_lock_assert(m, MA_OWNED);
object = m->object;
@@ -2056,15 +2083,42 @@ vm_page_cache(vm_page_t m)
* Remove the page from the object's collection of resident
* pages.
*/
- if (m != object->root)
- vm_page_splay(m->pindex, object->root);
- if (m->left == NULL)
- root = m->right;
- else {
- root = vm_page_splay(m->pindex, m->left);
- root->right = m->right;
+ if ((next = TAILQ_NEXT(m, listq)) != NULL && next->left == m) {
+ /*
+ * Since the page's successor in the list is also its parent
+ * in the tree, its right subtree must be empty.
+ */
+ next->left = m->left;
+ KASSERT(m->right == NULL,
+ ("vm_page_cache: page %p has right child", m));
+ } else if ((prev = TAILQ_PREV(m, pglist, listq)) != NULL &&
+ prev->right == m) {
+ /*
+ * Since the page's predecessor in the list is also its parent
+ * in the tree, its left subtree must be empty.
+ */
+ KASSERT(m->left == NULL,
+ ("vm_page_cache: page %p has left child", m));
+ prev->right = m->right;
+ } else {
+ if (m != object->root)
+ vm_page_splay(m->pindex, object->root);
+ if (m->left == NULL)
+ root = m->right;
+ else if (m->right == NULL)
+ root = m->left;
+ else {
+ /*
+ * Move the page's successor to the root, because
+ * pages are usually removed in ascending order.
+ */
+ if (m->right != next)
+ vm_page_splay(m->pindex, m->right);
+ next->left = m->left;
+ root = next;
+ }
+ object->root = root;
}
- object->root = root;
TAILQ_REMOVE(&object->memq, m, listq);
object->resident_page_count--;
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