The synchronization provided by vm object locking has eliminated the

need for most calls to vm_page_busy().  Specifically, most calls to
vm_page_busy() occur immediately prior to a call to vm_page_remove().
In such cases, the containing vm object is locked across both calls.
Consequently, the setting of the vm page's PG_BUSY flag is not even
visible to other threads that are following the synchronization
protocol.

This change (1) eliminates the calls to vm_page_busy() that
immediately precede a call to vm_page_remove() or functions, such as
vm_page_free() and vm_page_rename(), that call it and (2) relaxes the
requirement in vm_page_remove() that the vm page's PG_BUSY flag is
set.  Now, the vm page's PG_BUSY flag is set only when the vm object
lock is released while the vm page is still in transition.  Typically,
this is when it is undergoing I/O.

1 files changed, 0 insertions, 2 deletions

diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index 3d21c1f..cfb9eab 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -823,7 +823,6 @@ rescan0:
 			/*
 			 * Invalid pages can be easily freed
 			 */
-			vm_page_busy(m);
 			pmap_remove_all(m);
 			vm_page_free(m);
 			cnt.v_dfree++;
@@ -1107,7 +1106,6 @@ unlock_and_continue:
 		cache_rover = (m->pc + PQ_PRIME2) & PQ_L2_MASK;
 		object = m->object;
 		VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
-		vm_page_busy(m);
 		vm_page_free(m);
 		VM_OBJECT_UNLOCK(object);
 		cnt.v_dfree++;