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Commit f4155eff authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'RDS-optimized-notification-for-zerocopy-completion' 



Sowmini Varadhan says:

====================
RDS: optimized notification for zerocopy completion

Resending with acked-by additions: previous attempt does not show
up in Patchwork. This time with a new mail Message-Id.

RDS applications use predominantly request-response, transacation
based IPC, so that ingress and egress traffic are well-balanced,
and it is possible/desirable to reduce system-call overhead by
piggybacking the notifications for zerocopy completion response
with data.

Moreover, it has been pointed out that socket functions block
if sk_err is non-zero, thus if the RDS code does not plan/need
to use sk_error_queue path for completion notification, it
is preferable to remove the sk_errror_queue related paths in
RDS.

Both of these goals are implemented in this series.

v2: removed sk_error_queue support
v3: incorporated additional code review comments (details in each patch)
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents c1de13bb 6f3899e6

include/uapi/linux/errqueue.h

+0 −2
Original line number Diff line number Diff line
@@ -20,13 +20,11 @@ struct sock_extended_err { 
#define SO_EE_ORIGIN_ICMP6	3

#define SO_EE_ORIGIN_TXSTATUS	4

#define SO_EE_ORIGIN_ZEROCOPY	5

#define SO_EE_ORIGIN_ZCOOKIE	6

#define SO_EE_ORIGIN_TIMESTAMPING SO_EE_ORIGIN_TXSTATUS



#define SO_EE_OFFENDER(ee)	((struct sockaddr*)((ee)+1))



#define SO_EE_CODE_ZEROCOPY_COPIED	1

#define	SO_EE_ORIGIN_MAX_ZCOOKIES	8



/**

 *	struct scm_timestamping - timestamps exposed through cmsg

include/uapi/linux/rds.h

+7 −0
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ 
#define RDS_CMSG_MASKED_ATOMIC_CSWP	9

#define RDS_CMSG_RXPATH_LATENCY		11

#define	RDS_CMSG_ZCOPY_COOKIE		12

#define	RDS_CMSG_ZCOPY_COMPLETION	13



#define RDS_INFO_FIRST			10000

#define RDS_INFO_COUNTERS		10000
@@ -317,6 +318,12 @@ struct rds_rdma_notify { 
#define RDS_RDMA_DROPPED	3

#define RDS_RDMA_OTHER_ERROR	4



#define	RDS_MAX_ZCOOKIES	8

struct rds_zcopy_cookies {

	__u32 num;

	__u32 cookies[RDS_MAX_ZCOOKIES];

};



/*

 * Common set of flags for all RDMA related structs

 */

net/rds/af_rds.c

+5 −2
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ static int rds_release(struct socket *sock) 
	rds_send_drop_to(rs, NULL);

	rds_rdma_drop_keys(rs);

	rds_notify_queue_get(rs, NULL);

	__skb_queue_purge(&rs->rs_zcookie_queue);



	spin_lock_bh(&rds_sock_lock);

	list_del_init(&rs->rs_item);
@@ -144,7 +145,7 @@ static int rds_getname(struct socket *sock, struct sockaddr *uaddr, 
 *  -	to signal that a previously congested destination may have become

 *	uncongested

 *  -	A notification has been queued to the socket (this can be a congestion

 *	update, or a RDMA completion).

 *	update, or a RDMA completion, or a MSG_ZEROCOPY completion).

 *

 * EPOLLOUT is asserted if there is room on the send queue. This does not mean

 * however, that the next sendmsg() call will succeed. If the application tries
@@ -178,7 +179,8 @@ static __poll_t rds_poll(struct file *file, struct socket *sock, 
		spin_unlock(&rs->rs_lock);

	}

	if (!list_empty(&rs->rs_recv_queue) ||

	    !list_empty(&rs->rs_notify_queue))

	    !list_empty(&rs->rs_notify_queue) ||

	    !skb_queue_empty(&rs->rs_zcookie_queue))

		mask |= (EPOLLIN | EPOLLRDNORM);

	if (rs->rs_snd_bytes < rds_sk_sndbuf(rs))

		mask |= (EPOLLOUT | EPOLLWRNORM);
@@ -513,6 +515,7 @@ static int __rds_create(struct socket *sock, struct sock *sk, int protocol) 
	INIT_LIST_HEAD(&rs->rs_recv_queue);

	INIT_LIST_HEAD(&rs->rs_notify_queue);

	INIT_LIST_HEAD(&rs->rs_cong_list);

	skb_queue_head_init(&rs->rs_zcookie_queue);

	spin_lock_init(&rs->rs_rdma_lock);

	rs->rs_rdma_keys = RB_ROOT;

	rs->rs_rx_traces = 0;

net/rds/message.c

+16 −22
Original line number Diff line number Diff line
@@ -58,32 +58,26 @@ EXPORT_SYMBOL_GPL(rds_message_addref); 


static inline bool skb_zcookie_add(struct sk_buff *skb, u32 cookie)

{

	struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);

	int ncookies;

	u32 *ptr;

	struct rds_zcopy_cookies *ck = (struct rds_zcopy_cookies *)skb->cb;

	int ncookies = ck->num;



	if (serr->ee.ee_origin != SO_EE_ORIGIN_ZCOOKIE)

	if (ncookies == RDS_MAX_ZCOOKIES)

		return false;

	ncookies = serr->ee.ee_data;

	if (ncookies == SO_EE_ORIGIN_MAX_ZCOOKIES)

		return false;

	ptr = skb_put(skb, sizeof(u32));

	*ptr = cookie;

	serr->ee.ee_data = ++ncookies;

	ck->cookies[ncookies] = cookie;

	ck->num =  ++ncookies;

	return true;

}



static void rds_rm_zerocopy_callback(struct rds_sock *rs,

				     struct rds_znotifier *znotif)

{

	struct sock *sk = rds_rs_to_sk(rs);

	struct sk_buff *skb, *tail;

	struct sock_exterr_skb *serr;

	unsigned long flags;

	struct sk_buff_head *q;

	u32 cookie = znotif->z_cookie;

	struct rds_zcopy_cookies *ck;



	q = &sk->sk_error_queue;

	q = &rs->rs_zcookie_queue;

	spin_lock_irqsave(&q->lock, flags);

	tail = skb_peek_tail(q);
@@ -91,22 +85,19 @@ static void rds_rm_zerocopy_callback(struct rds_sock *rs, 
		spin_unlock_irqrestore(&q->lock, flags);

		mm_unaccount_pinned_pages(&znotif->z_mmp);

		consume_skb(rds_skb_from_znotifier(znotif));

		sk->sk_error_report(sk);

		/* caller invokes rds_wake_sk_sleep() */

		return;

	}



	skb = rds_skb_from_znotifier(znotif);

	serr = SKB_EXT_ERR(skb);

	memset(&serr->ee, 0, sizeof(serr->ee));

	serr->ee.ee_errno = 0;

	serr->ee.ee_origin = SO_EE_ORIGIN_ZCOOKIE;

	serr->ee.ee_info = 0;

	ck = (struct rds_zcopy_cookies *)skb->cb;

	memset(ck, 0, sizeof(*ck));

	WARN_ON(!skb_zcookie_add(skb, cookie));



	__skb_queue_tail(q, skb);



	spin_unlock_irqrestore(&q->lock, flags);

	sk->sk_error_report(sk);

	/* caller invokes rds_wake_sk_sleep() */



	mm_unaccount_pinned_pages(&znotif->z_mmp);

}
@@ -129,6 +120,7 @@ static void rds_message_purge(struct rds_message *rm) 
		if (rm->data.op_mmp_znotifier) {

			zcopy = true;

			rds_rm_zerocopy_callback(rs, rm->data.op_mmp_znotifier);

			rds_wake_sk_sleep(rs);

			rm->data.op_mmp_znotifier = NULL;

		}

		sock_put(rds_rs_to_sk(rs));
@@ -362,10 +354,12 @@ int rds_message_copy_from_user(struct rds_message *rm, struct iov_iter *from, 
		int total_copied = 0;

		struct sk_buff *skb;



		skb = alloc_skb(SO_EE_ORIGIN_MAX_ZCOOKIES * sizeof(u32),

				GFP_KERNEL);

		skb = alloc_skb(0, GFP_KERNEL);

		if (!skb)

			return -ENOMEM;

		BUILD_BUG_ON(sizeof(skb->cb) <

			     max_t(int, sizeof(struct rds_znotifier),

				   sizeof(struct rds_zcopy_cookies)));

		rm->data.op_mmp_znotifier = RDS_ZCOPY_SKB(skb);

		if (mm_account_pinned_pages(&rm->data.op_mmp_znotifier->z_mmp,

					    length)) {

net/rds/rds.h

+2 −0
Original line number Diff line number Diff line
@@ -603,6 +603,8 @@ struct rds_sock { 
	/* Socket receive path trace points*/

	u8			rs_rx_traces;

	u8			rs_rx_trace[RDS_MSG_RX_DGRAM_TRACE_MAX];



	struct sk_buff_head	rs_zcookie_queue;

};



static inline struct rds_sock *rds_sk_to_rs(const struct sock *sk)