- Relax requirements for p_numthreads, p_threads, p_swtick, and p_nice from

   requiring the per-process spinlock to only requiring the process lock.
 - Reflect these changes in the proc.h documentation and consumers throughout
   the kernel.  This is a substantial reduction in locking cost for these
   fields and was made possible by recent changes to threading support.

3 files changed, 8 insertions, 22 deletions

diff --git a/sys/vm/vm_glue.c b/sys/vm/vm_glue.c
index a1157ed..9f9dc5a 100644
--- a/sys/vm/vm_glue.c
+++ b/sys/vm/vm_glue.c
@@ -338,6 +338,7 @@ vm_thread_new(struct thread *td, int pages)
 	 * Allocate an object for the kstack.
 	 */
 	ksobj = vm_object_allocate(OBJT_DEFAULT, pages);
+	
 	/*
 	 * Get a kernel virtual address for this thread's kstack.
 	 */
@@ -645,10 +646,8 @@ faultin(p)
 		FOREACH_THREAD_IN_PROC(p, td)
 			vm_thread_swapin(td);
 		PROC_LOCK(p);
-		PROC_SLOCK(p);
 		swapclear(p);
 		p->p_swtick = ticks;
-		PROC_SUNLOCK(p);
 
 		wakeup(&p->p_flag);
 
@@ -700,7 +699,6 @@ loop:
 			continue;
 		}
 		swtime = (ticks - p->p_swtick) / hz;
-		PROC_SLOCK(p);
 		FOREACH_THREAD_IN_PROC(p, td) {
 			/*
 			 * An otherwise runnable thread of a process
@@ -726,7 +724,6 @@ loop:
 			}
 			thread_unlock(td);
 		}
-		PROC_SUNLOCK(p);
 		PROC_UNLOCK(p);
 	}
 	sx_sunlock(&allproc_lock);
@@ -868,7 +865,7 @@ retry:
 		if (p->p_lock != 0 ||
 		    (p->p_flag & (P_STOPPED_SINGLE|P_TRACED|P_SYSTEM|P_WEXIT)
 		    ) != 0) {
-			goto nextproc2;
+			goto nextproc;
 		}
 		/*
 		 * only aiod changes vmspace, however it will be
@@ -876,7 +873,7 @@ retry:
 		 * for P_SYSTEM
 		 */
 		if ((p->p_flag & (P_INMEM|P_SWAPPINGOUT|P_SWAPPINGIN)) != P_INMEM)
-			goto nextproc2;
+			goto nextproc;
 
 		switch (p->p_state) {
 		default:
@@ -885,7 +882,6 @@ retry:
 			break;
 
 		case PRS_NORMAL:
-			PROC_SLOCK(p);
 			/*
 			 * do not swapout a realtime process
 			 * Check all the thread groups..
@@ -947,17 +943,14 @@ retry:
 				 (minslptime > swap_idle_threshold2))) {
 				if (swapout(p) == 0)
 					didswap++;
-				PROC_SUNLOCK(p);
 				PROC_UNLOCK(p);
 				vm_map_unlock(&vm->vm_map);
 				vmspace_free(vm);
 				sx_sunlock(&allproc_lock);
 				goto retry;
 			}
-nextproc:			
-			PROC_SUNLOCK(p);
 		}
-nextproc2:
+nextproc:
 		PROC_UNLOCK(p);
 		vm_map_unlock(&vm->vm_map);
 nextproc1:
@@ -980,7 +973,6 @@ swapclear(p)
 	struct thread *td;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
-	PROC_SLOCK_ASSERT(p, MA_OWNED);
 
 	FOREACH_THREAD_IN_PROC(p, td) {
 		thread_lock(td);
@@ -1002,7 +994,6 @@ swapout(p)
 	struct thread *td;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
-	PROC_SLOCK_ASSERT(p, MA_OWNED | MA_NOTRECURSED);
 #if defined(SWAP_DEBUG)
 	printf("swapping out %d\n", p->p_pid);
 #endif
@@ -1037,7 +1028,6 @@ swapout(p)
 	}
 	td = FIRST_THREAD_IN_PROC(p);
 	++td->td_ru.ru_nswap;
-	PROC_SUNLOCK(p);
 	PROC_UNLOCK(p);
 
 	/*
@@ -1050,7 +1040,6 @@ swapout(p)
 
 	PROC_LOCK(p);
 	p->p_flag &= ~P_SWAPPINGOUT;
-	PROC_SLOCK(p);
 	p->p_swtick = ticks;
 	return (0);
 }
diff --git a/sys/vm/vm_meter.c b/sys/vm/vm_meter.c
index d71eabf..c644631 100644
--- a/sys/vm/vm_meter.c
+++ b/sys/vm/vm_meter.c
@@ -130,13 +130,16 @@ vmtotal(SYSCTL_HANDLER_ARGS)
 	FOREACH_PROC_IN_SYSTEM(p) {
 		if (p->p_flag & P_SYSTEM)
 			continue;
+		PROC_LOCK(p);
 		PROC_SLOCK(p);
 		switch (p->p_state) {
 		case PRS_NEW:
 			PROC_SUNLOCK(p);
+			PROC_UNLOCK(p);
 			continue;
 			break;
 		default:
+			PROC_SUNLOCK(p);
 			FOREACH_THREAD_IN_PROC(p, td) {
 				thread_lock(td);
 				switch (td->td_state) {
@@ -164,7 +167,7 @@ vmtotal(SYSCTL_HANDLER_ARGS)
 				thread_unlock(td);
 			}
 		}
-		PROC_SUNLOCK(p);
+		PROC_UNLOCK(p);
 		/*
 		 * Note active objects.
 		 */
diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index bf899a6..a3ecc98 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1206,7 +1206,6 @@ unlock_and_continue:
 			 * If the process is in a non-running type state,
 			 * don't touch it.  Check all the threads individually.
 			 */
-			PROC_SLOCK(p);
 			breakout = 0;
 			FOREACH_THREAD_IN_PROC(p, td) {
 				thread_lock(td);
@@ -1219,7 +1218,6 @@ unlock_and_continue:
 				}
 				thread_unlock(td);
 			}
-			PROC_SUNLOCK(p);
 			if (breakout) {
 				PROC_UNLOCK(p);
 				continue;
@@ -1249,9 +1247,7 @@ unlock_and_continue:
 		sx_sunlock(&allproc_lock);
 		if (bigproc != NULL) {
 			killproc(bigproc, "out of swap space");
-			PROC_SLOCK(bigproc);
 			sched_nice(bigproc, PRIO_MIN);
-			PROC_SUNLOCK(bigproc);
 			PROC_UNLOCK(bigproc);
 			wakeup(&cnt.v_free_count);
 		}
@@ -1560,7 +1556,6 @@ vm_daemon()
 			 * if the process is in a non-running type state,
 			 * don't touch it.
 			 */
-			PROC_SLOCK(p);
 			breakout = 0;
 			FOREACH_THREAD_IN_PROC(p, td) {
 				thread_lock(td);
@@ -1573,7 +1568,6 @@ vm_daemon()
 				}
 				thread_unlock(td);
 			}
-			PROC_SUNLOCK(p);
 			if (breakout) {
 				PROC_UNLOCK(p);
 				continue;