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Commit ff3ac5c3 authored by Trond Myklebust's avatar Trond Myklebust Committed by J. Bruce Fields
Browse files

SUNRPC: Add a server side per-connection limit 



Allow the user to limit the number of requests serviced through a single
connection, to help prevent faster clients from starving slower clients.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: default avatarJ. Bruce Fields <bfields@redhat.com>
parent 4720b070

Documentation/kernel-parameters.txt

+6 −0
Original line number Diff line number Diff line
@@ -3832,6 +3832,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			using these two parameters to set the minimum and

			maximum port values.



	sunrpc.svc_rpc_per_connection_limit=

			[NFS,SUNRPC]

			Limit the number of requests that the server will

			process in parallel from a single connection.

			The default value is 0 (no limit).



	sunrpc.pool_mode=

			[NFS]

			Control how the NFS server code allocates CPUs to

include/linux/sunrpc/svc.h

+1 −0
Original line number Diff line number Diff line
@@ -268,6 +268,7 @@ struct svc_rqst { 
						 * cache pages */

#define	RQ_VICTIM	(5)			/* about to be shut down */

#define	RQ_BUSY		(6)			/* request is busy */

#define	RQ_DATA		(7)			/* request has data */

	unsigned long		rq_flags;	/* flags field */



	void *			rq_argp;	/* decoded arguments */

include/linux/sunrpc/svc_xprt.h

+1 −0
Original line number Diff line number Diff line
@@ -69,6 +69,7 @@ struct svc_xprt { 


	struct svc_serv		*xpt_server;	/* service for transport */

	atomic_t    	    	xpt_reserved;	/* space on outq that is rsvd */

	atomic_t		xpt_nr_rqsts;	/* Number of requests */

	struct mutex		xpt_mutex;	/* to serialize sending data */

	spinlock_t		xpt_lock;	/* protects sk_deferred

						 * and xpt_auth_cache */

net/sunrpc/svc_xprt.c

+36 −3
Original line number Diff line number Diff line
@@ -21,6 +21,10 @@ 


#define RPCDBG_FACILITY	RPCDBG_SVCXPRT



static unsigned int svc_rpc_per_connection_limit __read_mostly;

module_param(svc_rpc_per_connection_limit, uint, 0644);





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);
@@ -329,12 +333,41 @@ char *svc_print_addr(struct svc_rqst *rqstp, char *buf, size_t len) 
}

EXPORT_SYMBOL_GPL(svc_print_addr);



static bool svc_xprt_slots_in_range(struct svc_xprt *xprt)

{

	unsigned int limit = svc_rpc_per_connection_limit;

	int nrqsts = atomic_read(&xprt->xpt_nr_rqsts);



	return limit == 0 || (nrqsts >= 0 && nrqsts < limit);

}



static bool svc_xprt_reserve_slot(struct svc_rqst *rqstp, struct svc_xprt *xprt)

{

	if (!test_bit(RQ_DATA, &rqstp->rq_flags)) {

		if (!svc_xprt_slots_in_range(xprt))

			return false;

		atomic_inc(&xprt->xpt_nr_rqsts);

		set_bit(RQ_DATA, &rqstp->rq_flags);

	}

	return true;

}



static void svc_xprt_release_slot(struct svc_rqst *rqstp)

{

	struct svc_xprt	*xprt = rqstp->rq_xprt;

	if (test_and_clear_bit(RQ_DATA, &rqstp->rq_flags)) {

		atomic_dec(&xprt->xpt_nr_rqsts);

		svc_xprt_enqueue(xprt);

	}

}



static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt)

{

	if (xprt->xpt_flags & ((1<<XPT_CONN)|(1<<XPT_CLOSE)))

		return true;

	if (xprt->xpt_flags & ((1<<XPT_DATA)|(1<<XPT_DEFERRED))) {

		if (xprt->xpt_ops->xpo_has_wspace(xprt))

		if (xprt->xpt_ops->xpo_has_wspace(xprt) &&

		    svc_xprt_slots_in_range(xprt))

			return true;

		trace_svc_xprt_no_write_space(xprt);

		return false;
@@ -516,8 +549,8 @@ static void svc_xprt_release(struct svc_rqst *rqstp) 


	rqstp->rq_res.head[0].iov_len = 0;

	svc_reserve(rqstp, 0);

	svc_xprt_release_slot(rqstp);

	rqstp->rq_xprt = NULL;



	svc_xprt_put(xprt);

}
@@ -785,7 +818,7 @@ static int svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt) 
			svc_add_new_temp_xprt(serv, newxpt);

		else

			module_put(xprt->xpt_class->xcl_owner);

	} else {

	} else if (svc_xprt_reserve_slot(rqstp, xprt)) {

		/* XPT_DATA|XPT_DEFERRED case: */

		dprintk("svc: server %p, pool %u, transport %p, inuse=%d\n",

			rqstp, rqstp->rq_pool->sp_id, xprt,