Revert "knfsd: avoid overloading the CPU scheduler with enormous load…

… averages"

This reverts commit 59a252f.

This helps in an entirely cached workload but not necessarily in
workloads that require waiting on disk.

Conflicts:

	include/linux/sunrpc/svc.h
	net/sunrpc/svc_xprt.c

Reported-by: Simon Kirby <[email protected]>
Tested-by: Jesper Krogh <[email protected]>
Signed-off-by: J. Bruce Fields <[email protected]>

include/linux/sunrpc/svc.h

@@ -29,7 +29,6 @@ struct svc_pool_stats {
 	unsigned long	packets;
 	unsigned long	sockets_queued;
 	unsigned long	threads_woken;
-	unsigned long	overloads_avoided;
 	unsigned long	threads_timedout;
 };
 
@@ -50,7 +49,6 @@ struct svc_pool {
 	struct list_head	sp_sockets;	/* pending sockets */
 	unsigned int		sp_nrthreads;	/* # of threads in pool */
 	struct list_head	sp_all_threads;	/* all server threads */
-	int			sp_nwaking;	/* number of threads woken but not yet active */
 	struct svc_pool_stats	sp_stats;	/* statistics on pool operation */
 } ____cacheline_aligned_in_smp;
 
@@ -284,7 +282,6 @@ struct svc_rqst {
 						 * cache pages */
 	wait_queue_head_t	rq_wait;	/* synchronization */
 	struct task_struct	*rq_task;	/* service thread */
-	int			rq_waking;	/* 1 if thread is being woken */
 };
 
 /*

net/sunrpc/svc_xprt.c

@@ -16,8 +16,6 @@
 
 #define RPCDBG_FACILITY	RPCDBG_SVCXPRT
 
-#define SVC_MAX_WAKING 5
-
 static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt);
 static int svc_deferred_recv(struct svc_rqst *rqstp);
 static struct cache_deferred_req *svc_defer(struct cache_req *req);
@@ -306,7 +304,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 	struct svc_pool *pool;
 	struct svc_rqst	*rqstp;
 	int cpu;
-	int thread_avail;
 
 	if (!(xprt->xpt_flags &
 	      ((1<<XPT_CONN)|(1<<XPT_DATA)|(1<<XPT_CLOSE)|(1<<XPT_DEFERRED))))
@@ -318,6 +315,12 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 
 	spin_lock_bh(&pool->sp_lock);
 
+	if (!list_empty(&pool->sp_threads) &&
+	    !list_empty(&pool->sp_sockets))
+		printk(KERN_ERR
+		       "svc_xprt_enqueue: "
+		       "threads and transports both waiting??\n");
+
 	if (test_bit(XPT_DEAD, &xprt->xpt_flags)) {
 		/* Don't enqueue dead transports */
 		dprintk("svc: transport %p is dead, not enqueued\n", xprt);
@@ -358,15 +361,7 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 	}
 
  process:
-	/* Work out whether threads are available */
-	thread_avail = !list_empty(&pool->sp_threads);	/* threads are asleep */
-	if (pool->sp_nwaking >= SVC_MAX_WAKING) {
-		/* too many threads are runnable and trying to wake up */
-		thread_avail = 0;
-		pool->sp_stats.overloads_avoided++;
-	}
-
-	if (thread_avail) {
+	if (!list_empty(&pool->sp_threads)) {
 		rqstp = list_entry(pool->sp_threads.next,
 				   struct svc_rqst,
 				   rq_list);
@@ -381,8 +376,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 		svc_xprt_get(xprt);
 		rqstp->rq_reserved = serv->sv_max_mesg;
 		atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
-		rqstp->rq_waking = 1;
-		pool->sp_nwaking++;
 		pool->sp_stats.threads_woken++;
 		BUG_ON(xprt->xpt_pool != pool);
 		wake_up(&rqstp->rq_wait);
@@ -651,11 +644,6 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 		return -EINTR;
 
 	spin_lock_bh(&pool->sp_lock);
-	if (rqstp->rq_waking) {
-		rqstp->rq_waking = 0;
-		pool->sp_nwaking--;
-		BUG_ON(pool->sp_nwaking < 0);
-	}
 	xprt = svc_xprt_dequeue(pool);
 	if (xprt) {
 		rqstp->rq_xprt = xprt;
@@ -1204,16 +1192,15 @@ static int svc_pool_stats_show(struct seq_file *m, void *p)
 	struct svc_pool *pool = p;
 
 	if (p == SEQ_START_TOKEN) {
-		seq_puts(m, "# pool packets-arrived sockets-enqueued threads-woken overloads-avoided threads-timedout\n");
+		seq_puts(m, "# pool packets-arrived sockets-enqueued threads-woken threads-timedout\n");
 		return 0;
 	}
 
-	seq_printf(m, "%u %lu %lu %lu %lu %lu\n",
+	seq_printf(m, "%u %lu %lu %lu %lu\n",
 		pool->sp_id,
 		pool->sp_stats.packets,
 		pool->sp_stats.sockets_queued,
 		pool->sp_stats.threads_woken,
-		pool->sp_stats.overloads_avoided,
 		pool->sp_stats.threads_timedout);
 
 	return 0;