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, 1 deletions

diff --git a/sys/sparc64/sparc64/pmap.c b/sys/sparc64/sparc64/pmap.c
index f76a45c1..c07d5d2 100644
--- a/sys/sparc64/sparc64/pmap.c
+++ b/sys/sparc64/sparc64/pmap.c
@@ -1087,7 +1087,6 @@ pmap_release(pmap_t pm)
 		vm_page_lock_queues();
 		if (vm_page_sleep_if_busy(m, FALSE, "pmaprl"))
 			continue;
-		vm_page_busy(m);
 		KASSERT(m->hold_count == 0,
 		    ("pmap_release: freeing held tsb page"));
 		m->md.pmap = NULL;