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Speed up vm_page_cache() and vm_page_remove() by checking for a few

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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
This commit is contained in:
Alan Cox 2011-10-25 16:35:08 +00:00
parent 07d7662678
commit 9c60ca3238
1 changed files with 72 additions and 18 deletions
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90
sys/vm/vm_page.c
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@ -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--;