Commit a80a8461 authored by NeilBrown's avatar NeilBrown Committed by Trond Myklebust
Browse files

SUNRPC: remove scheduling boost for "SWAPPER" tasks. 



Currently, tasks marked as "swapper" tasks get put to the front of
non-priority rpc_queues, and are sorted earlier than non-swapper tasks on
the transport's ->xmit_queue.

This is pointless as currently *all* tasks for a mount that has swap
enabled on *any* file are marked as "swapper" tasks.  So the net result
is that the non-priority rpc_queues are reverse-ordered (LIFO).

This scheduling boost is not necessary to avoid deadlocks, and hurts
fairness, so remove it.  If there were a need to expedite some requests,
the tk_priority mechanism is a more appropriate tool.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent a7210354

net/sunrpc/sched.c

+0 −7
Original line number Diff line number Diff line
@@ -186,11 +186,6 @@ static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, 


/*

 * Add new request to wait queue.

 *

 * Swapper tasks always get inserted at the head of the queue.

 * This should avoid many nasty memory deadlocks and hopefully

 * improve overall performance.

 * Everyone else gets appended to the queue to ensure proper FIFO behavior.

 */

static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,

		struct rpc_task *task,
@@ -199,8 +194,6 @@ static void __rpc_add_wait_queue(struct rpc_wait_queue *queue, 
	INIT_LIST_HEAD(&task->u.tk_wait.timer_list);

	if (RPC_IS_PRIORITY(queue))

		__rpc_add_wait_queue_priority(queue, task, queue_priority);

	else if (RPC_IS_SWAPPER(task))

		list_add(&task->u.tk_wait.list, &queue->tasks[0]);

	else

		list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);

	task->tk_waitqueue = queue;

net/sunrpc/xprt.c

+0 −11
Original line number Diff line number Diff line
@@ -1354,17 +1354,6 @@ xprt_request_enqueue_transmit(struct rpc_task *task) 
				INIT_LIST_HEAD(&req->rq_xmit2);

				goto out;

			}

		} else if (RPC_IS_SWAPPER(task)) {

			list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {

				if (pos->rq_cong || pos->rq_bytes_sent)

					continue;

				if (RPC_IS_SWAPPER(pos->rq_task))

					continue;

				/* Note: req is added _before_ pos */

				list_add_tail(&req->rq_xmit, &pos->rq_xmit);

				INIT_LIST_HEAD(&req->rq_xmit2);

				goto out;

			}

		} else if (!req->rq_seqno) {

			list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {

				if (pos->rq_task->tk_owner != task->tk_owner)