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

This reverts commit 59a252ff8c0f2fa32c896f69d56ae33e641ce7ad.

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 <sim@hostway.ca>
Tested-by: Jesper Krogh <jesper@krogh.cc>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

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;