Commit 1c87a0c3 authored by Jeff Layton's avatar Jeff Layton Committed by Chuck Lever
Browse files

nfsd: adjust number of running nfsd threads based on activity 



nfsd() is changed to pass a timeout to svc_recv() when there is a min
number of threads set, and to handle error returns from it:

In the case of -ETIMEDOUT, if the service mutex can be taken (via
trylock), the thread becomes an RQ_VICTIM so that it will exit,
providing that the actual number of threads is above pool->sp_nrthrmin.

In the case of -EBUSY, if the actual number of threads is below
pool->sp_nrthrmax, it will attempt to start a new thread. This attempt
is gated on a new SP_TASK_STARTING pool flag that serializes thread
creation attempts within a pool, and further by mutex_trylock().

Neil says: "I think we want memory pressure to be able to push a thread
into returning -ETIMEDOUT.  That can come later."

Signed-off-by: default avatarNeilBrown <neil@brown.name>
Signed-off-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent a0022a38

fs/nfsd/nfssvc.c

+42 −1
Original line number Diff line number Diff line
@@ -882,9 +882,11 @@ static int 
nfsd(void *vrqstp)

{

	struct svc_rqst *rqstp = (struct svc_rqst *) vrqstp;

	struct svc_pool *pool = rqstp->rq_pool;

	struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list);

	struct net *net = perm_sock->xpt_net;

	struct nfsd_net *nn = net_generic(net, nfsd_net_id);

	bool have_mutex = false;



	/* At this point, the thread shares current->fs

	 * with the init process. We need to create files with the
@@ -902,7 +904,44 @@ nfsd(void *vrqstp) 
	 * The main request loop

	 */

	while (!svc_thread_should_stop(rqstp)) {

		svc_recv(rqstp, 0);

		switch (svc_recv(rqstp, 5 * HZ)) {

		case -ETIMEDOUT:

			/* No work arrived within the timeout window */

			if (mutex_trylock(&nfsd_mutex)) {

				if (pool->sp_nrthreads > pool->sp_nrthrmin) {

					trace_nfsd_dynthread_kill(net, pool);

					set_bit(RQ_VICTIM, &rqstp->rq_flags);

					have_mutex = true;

				} else {

					mutex_unlock(&nfsd_mutex);

				}

			} else {

				trace_nfsd_dynthread_trylock_fail(net, pool);

			}

			break;

		case -EBUSY:

			/* No idle threads; consider spawning another */

			if (pool->sp_nrthreads < pool->sp_nrthrmax) {

				if (mutex_trylock(&nfsd_mutex)) {

					if (pool->sp_nrthreads < pool->sp_nrthrmax) {

						int ret;



						trace_nfsd_dynthread_start(net, pool);

						ret = svc_new_thread(rqstp->rq_server, pool);

						if (ret)

							pr_notice_ratelimited("%s: unable to spawn new thread: %d\n",

									      __func__, ret);

					}

					mutex_unlock(&nfsd_mutex);

				} else {

					trace_nfsd_dynthread_trylock_fail(net, pool);

				}

			}

			clear_bit(SP_TASK_STARTING, &pool->sp_flags);

			break;

		default:

			break;

		}

		nfsd_file_net_dispose(nn);

	}
@@ -910,6 +949,8 @@ nfsd(void *vrqstp) 


	/* Release the thread */

	svc_exit_thread(rqstp);

	if (have_mutex)

		mutex_unlock(&nfsd_mutex);

	return 0;

}

fs/nfsd/trace.h

+35 −0
Original line number Diff line number Diff line
@@ -91,6 +91,41 @@ DEFINE_EVENT(nfsd_xdr_err_class, nfsd_##name##_err, \ 
DEFINE_NFSD_XDR_ERR_EVENT(garbage_args);

DEFINE_NFSD_XDR_ERR_EVENT(cant_encode);



DECLARE_EVENT_CLASS(nfsd_dynthread_class,

	TP_PROTO(

		const struct net *net,

		const struct svc_pool *pool

	),

	TP_ARGS(net, pool),

	TP_STRUCT__entry(

		__field(unsigned int, netns_ino)

		__field(unsigned int, pool_id)

		__field(unsigned int, nrthreads)

		__field(unsigned int, nrthrmin)

		__field(unsigned int, nrthrmax)

	),

	TP_fast_assign(

		__entry->netns_ino = net->ns.inum;

		__entry->pool_id = pool->sp_id;

		__entry->nrthreads = pool->sp_nrthreads;

		__entry->nrthrmin = pool->sp_nrthrmin;

		__entry->nrthrmax = pool->sp_nrthrmax;

	),

	TP_printk("pool=%u nrthreads=%u nrthrmin=%u nrthrmax=%u",

		__entry->pool_id, __entry->nrthreads,

		__entry->nrthrmin, __entry->nrthrmax

	)

);



#define DEFINE_NFSD_DYNTHREAD_EVENT(name) \

DEFINE_EVENT(nfsd_dynthread_class, nfsd_dynthread_##name, \

	TP_PROTO(const struct net *net, const struct svc_pool *pool), \

	TP_ARGS(net, pool))



DEFINE_NFSD_DYNTHREAD_EVENT(start);

DEFINE_NFSD_DYNTHREAD_EVENT(kill);

DEFINE_NFSD_DYNTHREAD_EVENT(trylock_fail);



#define show_nfsd_may_flags(x)						\

	__print_flags(x, "|",						\

		{ NFSD_MAY_EXEC,		"EXEC" },		\