mirror/freebsd
1
0
Fork 0
mirror of https://git.FreeBSD.org/src.git synced 2024-12-14 10:09:48 +00:00
Code Issues Releases Activity

Simplify vm_page_grab(): Don't bother with the generation check. If the

Browse Source 
vm object hasn't changed, the desired page will be at or near the root
of the vm object's splay tree, making vm_page_lookup() cheap.  (The only
lock required for vm_page_lookup() is already held.)  If, however, the
vm object has changed and retry was requested, eliminating the generation
check also eliminates a pointless acquisition and release of the page
queues lock.
This commit is contained in:
Alan Cox 2003-12-31 01:44:45 +00:00
parent 279b7e129f
commit bcdaad7fe7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=124012
1 changed files with 6 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
sys/vm/vm_page.c
View File

@ -1432,30 +1432,18 @@ vm_page_t
vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
{
vm_page_t m;
int s, generation;
VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
retrylookup:
if ((m = vm_page_lookup(object, pindex)) != NULL) {
vm_page_lock_queues();
if (m->busy || (m->flags & PG_BUSY)) {
generation = object->generation;
s = splvm();
while ((object->generation == generation) &&
(m->busy || (m->flags & PG_BUSY))) {
vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
VM_OBJECT_UNLOCK(object);
msleep(m, &vm_page_queue_mtx, PDROP | PVM, "pgrbwt", 0);
VM_OBJECT_LOCK(object);
if ((allocflags & VM_ALLOC_RETRY) == 0) {
splx(s);
return NULL;
}
vm_page_lock_queues();
}
vm_page_unlock_queues();
splx(s);
vm_page_flag_set(m, PG_WANTED | PG_REFERENCED);
VM_OBJECT_UNLOCK(object);
msleep(m, &vm_page_queue_mtx, PDROP | PVM, "pgrbwt", 0);
VM_OBJECT_LOCK(object);
if ((allocflags & VM_ALLOC_RETRY) == 0)
return (NULL);
goto retrylookup;
} else {
if (allocflags & VM_ALLOC_WIRED)