xen-netback: switch to NAPI + kthread 1:1 model

This patch implements 1:1 model netback. NAPI and kthread are utilized
to do the weight-lifting job:

- NAPI is used for guest side TX (host side RX)
- kthread is used for guest side RX (host side TX)

Xenvif and xen_netbk are made into one structure to reduce code size.

This model provides better scheduling fairness among vifs. It is also
prerequisite for implementing multiqueue for Xen netback.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 177 insertions, 430 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 91f163d03a4..44ccc674c02 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -70,116 +70,25 @@ module_param(fatal_skb_slots, uint, 0444);
  */
 #define XEN_NETBK_LEGACY_SLOTS_MAX XEN_NETIF_NR_SLOTS_MIN
 
-typedef unsigned int pending_ring_idx_t;
-#define INVALID_PENDING_RING_IDX (~0U)
-
-struct pending_tx_info {
-	struct xen_netif_tx_request req; /* coalesced tx request */
-	struct xenvif *vif;
-	pending_ring_idx_t head; /* head != INVALID_PENDING_RING_IDX
-				  * if it is head of one or more tx
-				  * reqs
-				  */
-};
-
-struct netbk_rx_meta {
-	int id;
-	int size;
-	int gso_size;
-};
-
-#define MAX_PENDING_REQS 256
-
-/* Discriminate from any valid pending_idx value. */
-#define INVALID_PENDING_IDX 0xFFFF
-
-#define MAX_BUFFER_OFFSET PAGE_SIZE
-
-struct xen_netbk {
-	wait_queue_head_t wq;
-	struct task_struct *task;
-
-	struct sk_buff_head rx_queue;
-	struct sk_buff_head tx_queue;
-
-	struct timer_list net_timer;
-
-	struct page *mmap_pages[MAX_PENDING_REQS];
-
-	pending_ring_idx_t pending_prod;
-	pending_ring_idx_t pending_cons;
-	struct list_head net_schedule_list;
-
-	/* Protect the net_schedule_list in netif. */
-	spinlock_t net_schedule_list_lock;
-
-	atomic_t netfront_count;
-
-	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
-	/* Coalescing tx requests before copying makes number of grant
-	 * copy ops greater or equal to number of slots required. In
-	 * worst case a tx request consumes 2 gnttab_copy.
-	 */
-	struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
-
-	u16 pending_ring[MAX_PENDING_REQS];
-
-	/*
-	 * Given MAX_BUFFER_OFFSET of 4096 the worst case is that each
-	 * head/fragment page uses 2 copy operations because it
-	 * straddles two buffers in the frontend.
-	 */
-	struct gnttab_copy grant_copy_op[2*XEN_NETIF_RX_RING_SIZE];
-	struct netbk_rx_meta meta[2*XEN_NETIF_RX_RING_SIZE];
-};
-
-static struct xen_netbk *xen_netbk;
-static int xen_netbk_group_nr;
-
 /*
  * If head != INVALID_PENDING_RING_IDX, it means this tx request is head of
  * one or more merged tx requests, otherwise it is the continuation of
  * previous tx request.
  */
-static inline int pending_tx_is_head(struct xen_netbk *netbk, RING_IDX idx)
-{
-	return netbk->pending_tx_info[idx].head != INVALID_PENDING_RING_IDX;
-}
-
-void xen_netbk_add_xenvif(struct xenvif *vif)
-{
-	int i;
-	int min_netfront_count;
-	int min_group = 0;
-	struct xen_netbk *netbk;
-
-	min_netfront_count = atomic_read(&xen_netbk[0].netfront_count);
-	for (i = 0; i < xen_netbk_group_nr; i++) {
-		int netfront_count = atomic_read(&xen_netbk[i].netfront_count);
-		if (netfront_count < min_netfront_count) {
-			min_group = i;
-			min_netfront_count = netfront_count;
-		}
-	}
-
-	netbk = &xen_netbk[min_group];
-
-	vif->netbk = netbk;
-	atomic_inc(&netbk->netfront_count);
-}
-
-void xen_netbk_remove_xenvif(struct xenvif *vif)
+static inline int pending_tx_is_head(struct xenvif *vif, RING_IDX idx)
 {
-	struct xen_netbk *netbk = vif->netbk;
-	vif->netbk = NULL;
-	atomic_dec(&netbk->netfront_count);
+	return vif->pending_tx_info[idx].head != INVALID_PENDING_RING_IDX;
 }
 
-static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
+static void xen_netbk_idx_release(struct xenvif *vif, u16 pending_idx,
 				  u8 status);
 static void make_tx_response(struct xenvif *vif,
 			     struct xen_netif_tx_request *txp,
 			     s8       st);
+
+static inline int tx_work_todo(struct xenvif *vif);
+static inline int rx_work_todo(struct xenvif *vif);
+
 static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
 					     u16      id,
 					     s8       st,
@@ -187,16 +96,16 @@ static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
 					     u16      size,
 					     u16      flags);
 
-static inline unsigned long idx_to_pfn(struct xen_netbk *netbk,
+static inline unsigned long idx_to_pfn(struct xenvif *vif,
 				       u16 idx)
 {
-	return page_to_pfn(netbk->mmap_pages[idx]);
+	return page_to_pfn(vif->mmap_pages[idx]);
 }
 
-static inline unsigned long idx_to_kaddr(struct xen_netbk *netbk,
+static inline unsigned long idx_to_kaddr(struct xenvif *vif,
 					 u16 idx)
 {
-	return (unsigned long)pfn_to_kaddr(idx_to_pfn(netbk, idx));
+	return (unsigned long)pfn_to_kaddr(idx_to_pfn(vif, idx));
 }
 
 /*
@@ -224,15 +133,10 @@ static inline pending_ring_idx_t pending_index(unsigned i)
 	return i & (MAX_PENDING_REQS-1);
 }
 
-static inline pending_ring_idx_t nr_pending_reqs(struct xen_netbk *netbk)
+static inline pending_ring_idx_t nr_pending_reqs(struct xenvif *vif)
 {
 	return MAX_PENDING_REQS -
-		netbk->pending_prod + netbk->pending_cons;
-}
-
-static void xen_netbk_kick_thread(struct xen_netbk *netbk)
-{
-	wake_up(&netbk->wq);
+		vif->pending_prod + vif->pending_cons;
 }
 
 static int max_required_rx_slots(struct xenvif *vif)
@@ -364,15 +268,15 @@ struct netrx_pending_operations {
 	unsigned copy_prod, copy_cons;
 	unsigned meta_prod, meta_cons;
 	struct gnttab_copy *copy;
-	struct netbk_rx_meta *meta;
+	struct xenvif_rx_meta *meta;
 	int copy_off;
 	grant_ref_t copy_gref;
 };
 
-static struct netbk_rx_meta *get_next_rx_buffer(struct xenvif *vif,
-						struct netrx_pending_operations *npo)
+static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif *vif,
+						 struct netrx_pending_operations *npo)
 {
-	struct netbk_rx_meta *meta;
+	struct xenvif_rx_meta *meta;
 	struct xen_netif_rx_request *req;
 
 	req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
@@ -398,7 +302,7 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
 				unsigned long offset, int *head)
 {
 	struct gnttab_copy *copy_gop;
-	struct netbk_rx_meta *meta;
+	struct xenvif_rx_meta *meta;
 	unsigned long bytes;
 
 	/* Data must not cross a page boundary. */
@@ -434,15 +338,15 @@ static void netbk_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
 
 		copy_gop = npo->copy + npo->copy_prod++;
 		copy_gop->flags = GNTCOPY_dest_gref;
+		copy_gop->len = bytes;
+
 		copy_gop->source.domid = DOMID_SELF;
 		copy_gop->source.u.gmfn = virt_to_mfn(page_address(page));
-
 		copy_gop->source.offset = offset;
-		copy_gop->dest.domid = vif->domid;
 
+		copy_gop->dest.domid = vif->domid;
 		copy_gop->dest.offset = npo->copy_off;
 		copy_gop->dest.u.ref = npo->copy_gref;
-		copy_gop->len = bytes;
 
 		npo->copy_off += bytes;
 		meta->size += bytes;
@@ -485,7 +389,7 @@ static int netbk_gop_skb(struct sk_buff *skb,
 	int nr_frags = skb_shinfo(skb)->nr_frags;
 	int i;
 	struct xen_netif_rx_request *req;
-	struct netbk_rx_meta *meta;
+	struct xenvif_rx_meta *meta;
 	unsigned char *data;
 	int head = 1;
 	int old_meta_prod;
@@ -565,7 +469,7 @@ static int netbk_check_gop(struct xenvif *vif, int nr_meta_slots,
 }
 
 static void netbk_add_frag_responses(struct xenvif *vif, int status,
-				     struct netbk_rx_meta *meta,
+				     struct xenvif_rx_meta *meta,
 				     int nr_meta_slots)
 {
 	int i;
@@ -594,9 +498,13 @@ struct skb_cb_overlay {
 	int meta_slots_used;
 };
 
-static void xen_netbk_rx_action(struct xen_netbk *netbk)
+static void xen_netbk_kick_thread(struct xenvif *vif)
+{
+	wake_up(&vif->wq);
+}
+
+void xen_netbk_rx_action(struct xenvif *vif)
 {
-	struct xenvif *vif = NULL, *tmp;
 	s8 status;
 	u16 flags;
 	struct xen_netif_rx_response *resp;
@@ -608,17 +516,18 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 	int count;
 	unsigned long offset;
 	struct skb_cb_overlay *sco;
+	int need_to_notify = 0;
 
 	struct netrx_pending_operations npo = {
-		.copy  = netbk->grant_copy_op,
-		.meta  = netbk->meta,
+		.copy  = vif->grant_copy_op,
+		.meta  = vif->meta,
 	};
 
 	skb_queue_head_init(&rxq);
 
 	count = 0;
 
-	while ((skb = skb_dequeue(&netbk->rx_queue)) != NULL) {
+	while ((skb = skb_dequeue(&vif->rx_queue)) != NULL) {
 		vif = netdev_priv(skb->dev);
 		nr_frags = skb_shinfo(skb)->nr_frags;
 
@@ -635,27 +544,27 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 			break;
 	}
 
-	BUG_ON(npo.meta_prod > ARRAY_SIZE(netbk->meta));
+	BUG_ON(npo.meta_prod > ARRAY_SIZE(vif->meta));
 
 	if (!npo.copy_prod)
 		return;
 
-	BUG_ON(npo.copy_prod > ARRAY_SIZE(netbk->grant_copy_op));
-	gnttab_batch_copy(netbk->grant_copy_op, npo.copy_prod);
+	BUG_ON(npo.copy_prod > ARRAY_SIZE(vif->grant_copy_op));
+	gnttab_batch_copy(vif->grant_copy_op, npo.copy_prod);
 
 	while ((skb = __skb_dequeue(&rxq)) != NULL) {
 		sco = (struct skb_cb_overlay *)skb->cb;
 
 		vif = netdev_priv(skb->dev);
 
-		if (netbk->meta[npo.meta_cons].gso_size && vif->gso_prefix) {
+		if (vif->meta[npo.meta_cons].gso_size && vif->gso_prefix) {
 			resp = RING_GET_RESPONSE(&vif->rx,
-						vif->rx.rsp_prod_pvt++);
+						 vif->rx.rsp_prod_pvt++);
 
 			resp->flags = XEN_NETRXF_gso_prefix | XEN_NETRXF_more_data;
 
-			resp->offset = netbk->meta[npo.meta_cons].gso_size;
-			resp->id = netbk->meta[npo.meta_cons].id;
+			resp->offset = vif->meta[npo.meta_cons].gso_size;
+			resp->id = vif->meta[npo.meta_cons].id;
 			resp->status = sco->meta_slots_used;
 
 			npo.meta_cons++;
@@ -680,12 +589,12 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 			flags |= XEN_NETRXF_data_validated;
 
 		offset = 0;
-		resp = make_rx_response(vif, netbk->meta[npo.meta_cons].id,
+		resp = make_rx_response(vif, vif->meta[npo.meta_cons].id,
 					status, offset,
-					netbk->meta[npo.meta_cons].size,
+					vif->meta[npo.meta_cons].size,
 					flags);
 
-		if (netbk->meta[npo.meta_cons].gso_size && !vif->gso_prefix) {
+		if (vif->meta[npo.meta_cons].gso_size && !vif->gso_prefix) {
 			struct xen_netif_extra_info *gso =
 				(struct xen_netif_extra_info *)
 				RING_GET_RESPONSE(&vif->rx,
@@ -693,7 +602,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 
 			resp->flags |= XEN_NETRXF_extra_info;
 
-			gso->u.gso.size = netbk->meta[npo.meta_cons].gso_size;
+			gso->u.gso.size = vif->meta[npo.meta_cons].gso_size;
 			gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
 			gso->u.gso.pad = 0;
 			gso->u.gso.features = 0;
@@ -703,112 +612,33 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 		}
 
 		netbk_add_frag_responses(vif, status,
-					 netbk->meta + npo.meta_cons + 1,
+					 vif->meta + npo.meta_cons + 1,
 					 sco->meta_slots_used);
 
 		RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->rx, ret);
 
+		if (ret)
+			need_to_notify = 1;
+
 		xenvif_notify_tx_completion(vif);
 
-		if (ret && list_empty(&vif->notify_list))
-			list_add_tail(&vif->notify_list, &notify);
-		else
-			xenvif_put(vif);
 		npo.meta_cons += sco->meta_slots_used;
 		dev_kfree_skb(skb);
 	}
 
-	list_for_each_entry_safe(vif, tmp, &notify, notify_list) {
+	if (need_to_notify)
 		notify_remote_via_irq(vif->rx_irq);
-		list_del_init(&vif->notify_list);
-		xenvif_put(vif);
-	}
 
 	/* More work to do? */
-	if (!skb_queue_empty(&netbk->rx_queue) &&
-			!timer_pending(&netbk->net_timer))
-		xen_netbk_kick_thread(netbk);
+	if (!skb_queue_empty(&vif->rx_queue))
+		xen_netbk_kick_thread(vif);
 }
 
 void xen_netbk_queue_tx_skb(struct xenvif *vif, struct sk_buff *skb)
 {
-	struct xen_netbk *netbk = vif->netbk;
+	skb_queue_tail(&vif->rx_queue, skb);
 
-	skb_queue_tail(&netbk->rx_queue, skb);
-
-	xen_netbk_kick_thread(netbk);
-}
-
-static void xen_netbk_alarm(unsigned long data)
-{
-	struct xen_netbk *netbk = (struct xen_netbk *)data;
-	xen_netbk_kick_thread(netbk);
-}
-
-static int __on_net_schedule_list(struct xenvif *vif)
-{
-	return !list_empty(&vif->schedule_list);
-}
-
-/* Must be called with net_schedule_list_lock held */
-static void remove_from_net_schedule_list(struct xenvif *vif)
-{
-	if (likely(__on_net_schedule_list(vif))) {
-		list_del_init(&vif->schedule_list);
-		xenvif_put(vif);
-	}
-}
-
-static struct xenvif *poll_net_schedule_list(struct xen_netbk *netbk)
-{
-	struct xenvif *vif = NULL;
-
-	spin_lock_irq(&netbk->net_schedule_list_lock);
-	if (list_empty(&netbk->net_schedule_list))
-		goto out;
-
-	vif = list_first_entry(&netbk->net_schedule_list,
-			       struct xenvif, schedule_list);
-	if (!vif)
-		goto out;
-
-	xenvif_get(vif);
-
-	remove_from_net_schedule_list(vif);
-out:
-	spin_unlock_irq(&netbk->net_schedule_list_lock);
-	return vif;
-}
-
-void xen_netbk_schedule_xenvif(struct xenvif *vif)
-{
-	unsigned long flags;
-	struct xen_netbk *netbk = vif->netbk;
-
-	if (__on_net_schedule_list(vif))
-		goto kick;
-
-	spin_lock_irqsave(&netbk->net_schedule_list_lock, flags);
-	if (!__on_net_schedule_list(vif) &&
-	    likely(xenvif_schedulable(vif))) {
-		list_add_tail(&vif->schedule_list, &netbk->net_schedule_list);
-		xenvif_get(vif);
-	}
-	spin_unlock_irqrestore(&netbk->net_schedule_list_lock, flags);
-
-kick:
-	smp_mb();
-	if ((nr_pending_reqs(netbk) < (MAX_PENDING_REQS/2)) &&
-	    !list_empty(&netbk->net_schedule_list))
-		xen_netbk_kick_thread(netbk);
-}
-
-void xen_netbk_deschedule_xenvif(struct xenvif *vif)
-{
-	struct xen_netbk *netbk = vif->netbk;
-	spin_lock_irq(&netbk->net_schedule_list_lock);
-	remove_from_net_schedule_list(vif);
-	spin_unlock_irq(&netbk->net_schedule_list_lock);
+	xen_netbk_kick_thread(vif);
 }
 
 void xen_netbk_check_rx_xenvif(struct xenvif *vif)
@@ -818,7 +648,7 @@ void xen_netbk_check_rx_xenvif(struct xenvif *vif)
 	RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);
 
 	if (more_to_do)
-		xen_netbk_schedule_xenvif(vif);
+		napi_schedule(&vif->napi);
 }
 
 static void tx_add_credit(struct xenvif *vif)
@@ -860,15 +690,12 @@ static void netbk_tx_err(struct xenvif *vif,
 		txp = RING_GET_REQUEST(&vif->tx, cons++);
 	} while (1);
 	vif->tx.req_cons = cons;
-	xen_netbk_check_rx_xenvif(vif);
-	xenvif_put(vif);
 }
 
 static void netbk_fatal_tx_err(struct xenvif *vif)
 {
 	netdev_err(vif->dev, "fatal error; disabling device\n");
 	xenvif_carrier_off(vif);
-	xenvif_put(vif);
 }
 
 static int netbk_count_requests(struct xenvif *vif,
@@ -969,19 +796,20 @@ static int netbk_count_requests(struct xenvif *vif,
 	return slots;
 }
 
-static struct page *xen_netbk_alloc_page(struct xen_netbk *netbk,
+static struct page *xen_netbk_alloc_page(struct xenvif *vif,
 					 u16 pending_idx)
 {
 	struct page *page;
-	page = alloc_page(GFP_KERNEL|__GFP_COLD);
+
+	page = alloc_page(GFP_ATOMIC|__GFP_COLD);
 	if (!page)
 		return NULL;
-	netbk->mmap_pages[pending_idx] = page;
+	vif->mmap_pages[pending_idx] = page;
+
 	return page;
 }
 
-static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
-						  struct xenvif *vif,
+static struct gnttab_copy *xen_netbk_get_requests(struct xenvif *vif,
 						  struct sk_buff *skb,
 						  struct xen_netif_tx_request *txp,
 						  struct gnttab_copy *gop)
@@ -1012,9 +840,9 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 	for (shinfo->nr_frags = slot = start; slot < nr_slots;
 	     shinfo->nr_frags++) {
 		struct pending_tx_info *pending_tx_info =
-			netbk->pending_tx_info;
+			vif->pending_tx_info;
 
-		page = alloc_page(GFP_KERNEL|__GFP_COLD);
+		page = alloc_page(GFP_ATOMIC|__GFP_COLD);
 		if (!page)
 			goto err;
 
@@ -1049,21 +877,18 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 				gop->len = txp->size;
 				dst_offset += gop->len;
 
-				index = pending_index(netbk->pending_cons++);
+				index = pending_index(vif->pending_cons++);
 
-				pending_idx = netbk->pending_ring[index];
+				pending_idx = vif->pending_ring[index];
 
 				memcpy(&pending_tx_info[pending_idx].req, txp,
 				       sizeof(*txp));
-				xenvif_get(vif);
-
-				pending_tx_info[pending_idx].vif = vif;
 
 				/* Poison these fields, corresponding
 				 * fields for head tx req will be set
 				 * to correct values after the loop.
 				 */
-				netbk->mmap_pages[pending_idx] = (void *)(~0UL);
+				vif->mmap_pages[pending_idx] = (void *)(~0UL);
 				pending_tx_info[pending_idx].head =
 					INVALID_PENDING_RING_IDX;
 
@@ -1083,7 +908,7 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 		first->req.offset = 0;
 		first->req.size = dst_offset;
 		first->head = start_idx;
-		netbk->mmap_pages[head_idx] = page;
+		vif->mmap_pages[head_idx] = page;
 		frag_set_pending_idx(&frags[shinfo->nr_frags], head_idx);
 	}
 
@@ -1093,18 +918,18 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 err:
 	/* Unwind, freeing all pages and sending error responses. */
 	while (shinfo->nr_frags-- > start) {
-		xen_netbk_idx_release(netbk,
+		xen_netbk_idx_release(vif,
 				frag_get_pending_idx(&frags[shinfo->nr_frags]),
 				XEN_NETIF_RSP_ERROR);
 	}
 	/* The head too, if necessary. */
 	if (start)
-		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
+		xen_netbk_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
 
 	return NULL;
 }
 
-static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
+static int xen_netbk_tx_check_gop(struct xenvif *vif,
 				  struct sk_buff *skb,
 				  struct gnttab_copy **gopp)
 {
@@ -1119,7 +944,7 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 	/* Check status of header. */
 	err = gop->status;
 	if (unlikely(err))
-		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
+		xen_netbk_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
 
 	/* Skip first skb fragment if it is on same page as header fragment. */
 	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
@@ -1129,7 +954,7 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 		pending_ring_idx_t head;
 
 		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
-		tx_info = &netbk->pending_tx_info[pending_idx];
+		tx_info = &vif->pending_tx_info[pending_idx];
 		head = tx_info->head;
 
 		/* Check error status: if okay then remember grant handle. */
@@ -1137,18 +962,19 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 			newerr = (++gop)->status;
 			if (newerr)
 				break;
-			peek = netbk->pending_ring[pending_index(++head)];
-		} while (!pending_tx_is_head(netbk, peek));
+			peek = vif->pending_ring[pending_index(++head)];
+		} while (!pending_tx_is_head(vif, peek));
 
 		if (likely(!newerr)) {
 			/* Had a previous error? Invalidate this fragment. */
 			if (unlikely(err))
-				xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
+				xen_netbk_idx_release(vif, pending_idx,
+						      XEN_NETIF_RSP_OKAY);
 			continue;
 		}
 
 		/* Error on this fragment: respond to client with an error. */
-		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
+		xen_netbk_idx_release(vif, pending_idx, XEN_NETIF_RSP_ERROR);
 
 		/* Not the first error? Preceding frags already invalidated. */
 		if (err)
@@ -1156,10 +982,11 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 
 		/* First error: invalidate header and preceding fragments. */
 		pending_idx = *((u16 *)skb->data);
-		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
+		xen_netbk_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
 		for (j = start; j < i; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
-			xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
+			xen_netbk_idx_release(vif, pending_idx,
+					      XEN_NETIF_RSP_OKAY);
 		}
 
 		/* Remember the error: invalidate all subsequent fragments. */
@@ -1170,7 +997,7 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 	return err;
 }
 
-static void xen_netbk_fill_frags(struct xen_netbk *netbk, struct sk_buff *skb)
+static void xen_netbk_fill_frags(struct xenvif *vif, struct sk_buff *skb)
 {
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	int nr_frags = shinfo->nr_frags;
@@ -1184,16 +1011,16 @@ static void xen_netbk_fill_frags(struct xen_netbk *netbk, struct sk_buff *skb)
 
 		pending_idx = frag_get_pending_idx(frag);
 
-		txp = &netbk->pending_tx_info[pending_idx].req;
-		page = virt_to_page(idx_to_kaddr(netbk, pending_idx));
+		txp = &vif->pending_tx_info[pending_idx].req;
+		page = virt_to_page(idx_to_kaddr(vif, pending_idx));
 		__skb_fill_page_desc(skb, i, page, txp->offset, txp->size);
 		skb->len += txp->size;
 		skb->data_len += txp->size;
 		skb->truesize += txp->size;
 
 		/* Take an extra reference to offset xen_netbk_idx_release */
-		get_page(netbk->mmap_pages[pending_idx]);
-		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
+		get_page(vif->mmap_pages[pending_idx]);
+		xen_netbk_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
 	}
 }
 
@@ -1353,16 +1180,14 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
 	return false;
 }
 
-static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
+static unsigned xen_netbk_tx_build_gops(struct xenvif *vif)
 {
-	struct gnttab_copy *gop = netbk->tx_copy_ops, *request_gop;
+	struct gnttab_copy *gop = vif->tx_copy_ops, *request_gop;
 	struct sk_buff *skb;
 	int ret;
 
-	while ((nr_pending_reqs(netbk) + XEN_NETBK_LEGACY_SLOTS_MAX
-		< MAX_PENDING_REQS) &&
-		!list_empty(&netbk->net_schedule_list)) {
-		struct xenvif *vif;
+	while ((nr_pending_reqs(vif) + XEN_NETBK_LEGACY_SLOTS_MAX
+		< MAX_PENDING_REQS)) {
 		struct xen_netif_tx_request txreq;
 		struct xen_netif_tx_request txfrags[XEN_NETBK_LEGACY_SLOTS_MAX];
 		struct page *page;
@@ -1373,16 +1198,6 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 		unsigned int data_len;
 		pending_ring_idx_t index;
 
-		/* Get a netif from the list with work to do. */
-		vif = poll_net_schedule_list(netbk);
-		/* This can sometimes happen because the test of
-		 * list_empty(net_schedule_list) at the top of the
-		 * loop is unlocked.  Just go back and have another
-		 * look.
-		 */
-		if (!vif)
-			continue;
-
 		if (vif->tx.sring->req_prod - vif->tx.req_cons >
 		    XEN_NETIF_TX_RING_SIZE) {
 			netdev_err(vif->dev,
@@ -1395,10 +1210,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 		}
 
 		RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, work_to_do);
-		if (!work_to_do) {
-			xenvif_put(vif);
-			continue;
-		}
+		if (!work_to_do)
+			break;
 
 		idx = vif->tx.req_cons;
 		rmb(); /* Ensure that we see the request before we copy it. */
@@ -1406,10 +1219,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 
 		/* Credit-based scheduling. */
 		if (txreq.size > vif->remaining_credit &&
-		    tx_credit_exceeded(vif, txreq.size)) {
-			xenvif_put(vif);
-			continue;
-		}
+		    tx_credit_exceeded(vif, txreq.size))
+			break;
 
 		vif->remaining_credit -= txreq.size;
 
@@ -1422,12 +1233,12 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 							  work_to_do);
 			idx = vif->tx.req_cons;
 			if (unlikely(work_to_do < 0))
-				continue;
+				break;
 		}
 
 		ret = netbk_count_requests(vif, &txreq, txfrags, work_to_do);
 		if (unlikely(ret < 0))
-			continue;
+			break;
 
 		idx += ret;
 
@@ -1435,7 +1246,7 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 			netdev_dbg(vif->dev,
 				   "Bad packet size: %d\n", txreq.size);
 			netbk_tx_err(vif, &txreq, idx);
-			continue;
+			break;
 		}
 
 		/* No crossing a page as the payload mustn't fragment. */
@@ -1445,11 +1256,11 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 				   txreq.offset, txreq.size,
 				   (txreq.offset&~PAGE_MASK) + txreq.size);
 			netbk_fatal_tx_err(vif);
-			continue;
+			break;
 		}
 
-		index = pending_index(netbk->pending_cons);
-		pending_idx = netbk->pending_ring[index];
+		index = pending_index(vif->pending_cons);
+		pending_idx = vif->pending_ring[index];
 
 		data_len = (txreq.size > PKT_PROT_LEN &&
 			    ret < XEN_NETBK_LEGACY_SLOTS_MAX) ?
@@ -1474,16 +1285,16 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 			if (netbk_set_skb_gso(vif, skb, gso)) {
 				/* Failure in netbk_set_skb_gso is fatal. */
 				kfree_skb(skb);
-				continue;
+				break;
 			}
 		}
 
 		/* XXX could copy straight to head */
-		page = xen_netbk_alloc_page(netbk, pending_idx);
+		page = xen_netbk_alloc_page(vif, pending_idx);
 		if (!page) {
 			kfree_skb(skb);
 			netbk_tx_err(vif, &txreq, idx);
-			continue;
+			break;
 		}
 
 		gop->source.u.ref = txreq.gref;
@@ -1499,10 +1310,9 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 
 		gop++;
 
-		memcpy(&netbk->pending_tx_info[pending_idx].req,
+		memcpy(&vif->pending_tx_info[pending_idx].req,
 		       &txreq, sizeof(txreq));
-		netbk->pending_tx_info[pending_idx].vif = vif;
-		netbk->pending_tx_info[pending_idx].head = index;
+		vif->pending_tx_info[pending_idx].head = index;
 		*((u16 *)skb->data) = pending_idx;
 
 		__skb_put(skb, data_len);
@@ -1517,46 +1327,45 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 					     INVALID_PENDING_IDX);
 		}
 
-		netbk->pending_cons++;
+		vif->pending_cons++;
 
-		request_gop = xen_netbk_get_requests(netbk, vif,
-						     skb, txfrags, gop);
+		request_gop = xen_netbk_get_requests(vif, skb, txfrags, gop);
 		if (request_gop == NULL) {
 			kfree_skb(skb);
 			netbk_tx_err(vif, &txreq, idx);
-			continue;
+			break;
 		}
 		gop = request_gop;
 
-		__skb_queue_tail(&netbk->tx_queue, skb);
+		__skb_queue_tail(&vif->tx_queue, skb);
 
 		vif->tx.req_cons = idx;
-		xen_netbk_check_rx_xenvif(vif);
 
-		if ((gop-netbk->tx_copy_ops) >= ARRAY_SIZE(netbk->tx_copy_ops))
+		if ((gop-vif->tx_copy_ops) >= ARRAY_SIZE(vif->tx_copy_ops))
 			break;
 	}
 
-	return gop - netbk->tx_copy_ops;
+	return gop - vif->tx_copy_ops;
 }
 
-static void xen_netbk_tx_submit(struct xen_netbk *netbk)
+
+static int xen_netbk_tx_submit(struct xenvif *vif, int budget)
 {
-	struct gnttab_copy *gop = netbk->tx_copy_ops;
+	struct gnttab_copy *gop = vif->tx_copy_ops;
 	struct sk_buff *skb;
+	int work_done = 0;
 
-	while ((skb = __skb_dequeue(&netbk->tx_queue)) != NULL) {
+	while (work_done < budget &&
+	       (skb = __skb_dequeue(&vif->tx_queue)) != NULL) {
 		struct xen_netif_tx_request *txp;
-		struct xenvif *vif;
 		u16 pending_idx;
 		unsigned data_len;
 
 		pending_idx = *((u16 *)skb->data);
-		vif = netbk->pending_tx_info[pending_idx].vif;
-		txp = &netbk->pending_tx_info[pending_idx].req;
+		txp = &vif->pending_tx_info[pending_idx].req;
 
 		/* Check the remap error code. */
-		if (unlikely(xen_netbk_tx_check_gop(netbk, skb, &gop))) {
+		if (unlikely(xen_netbk_tx_check_gop(vif, skb, &gop))) {
 			netdev_dbg(vif->dev, "netback grant failed.\n");
 			skb_shinfo(skb)->nr_frags = 0;
 			kfree_skb(skb);
@@ -1565,7 +1374,7 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 
 		data_len = skb->len;
 		memcpy(skb->data,
-		       (void *)(idx_to_kaddr(netbk, pending_idx)|txp->offset),
+		       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
 		       data_len);
 		if (data_len < txp->size) {
 			/* Append the packet payload as a fragment. */
@@ -1573,7 +1382,8 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 			txp->size -= data_len;
 		} else {
 			/* Schedule a response immediately. */
-			xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
+			xen_netbk_idx_release(vif, pending_idx,
+					      XEN_NETIF_RSP_OKAY);
 		}
 
 		if (txp->flags & XEN_NETTXF_csum_blank)
@@ -1581,7 +1391,7 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 		else if (txp->flags & XEN_NETTXF_data_validated)
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 
-		xen_netbk_fill_frags(netbk, skb);
+		xen_netbk_fill_frags(vif, skb);
 
 		/*
 		 * If the initial fragment was < PKT_PROT_LEN then
@@ -1609,53 +1419,61 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 		vif->dev->stats.rx_bytes += skb->len;
 		vif->dev->stats.rx_packets++;
 
-		xenvif_receive_skb(vif, skb);
+		work_done++;
+
+		netif_receive_skb(skb);
 	}
+
+	return work_done;
 }
 
 /* Called after netfront has transmitted */
-static void xen_netbk_tx_action(struct xen_netbk *netbk)
+int xen_netbk_tx_action(struct xenvif *vif, int budget)
 {
 	unsigned nr_gops;
+	int work_done;
 
-	nr_gops = xen_netbk_tx_build_gops(netbk);
+	if (unlikely(!tx_work_todo(vif)))
+		return 0;
+
+	nr_gops = xen_netbk_tx_build_gops(vif);
 
 	if (nr_gops == 0)
-		return;
+		return 0;
+
+	gnttab_batch_copy(vif->tx_copy_ops, nr_gops);
 
-	gnttab_batch_copy(netbk->tx_copy_ops, nr_gops);
+	work_done = xen_netbk_tx_submit(vif, nr_gops);
 
-	xen_netbk_tx_submit(netbk);
+	return work_done;
 }
 
-static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
+static void xen_netbk_idx_release(struct xenvif *vif, u16 pending_idx,
 				  u8 status)
 {
-	struct xenvif *vif;
 	struct pending_tx_info *pending_tx_info;
 	pending_ring_idx_t head;
 	u16 peek; /* peek into next tx request */
 
-	BUG_ON(netbk->mmap_pages[pending_idx] == (void *)(~0UL));
+	BUG_ON(vif->mmap_pages[pending_idx] == (void *)(~0UL));
 
 	/* Already complete? */
-	if (netbk->mmap_pages[pending_idx] == NULL)
+	if (vif->mmap_pages[pending_idx] == NULL)
 		return;
 
-	pending_tx_info = &netbk->pending_tx_info[pending_idx];
+	pending_tx_info = &vif->pending_tx_info[pending_idx];
 
-	vif = pending_tx_info->vif;
 	head = pending_tx_info->head;
 
-	BUG_ON(!pending_tx_is_head(netbk, head));
-	BUG_ON(netbk->pending_ring[pending_index(head)] != pending_idx);
+	BUG_ON(!pending_tx_is_head(vif, head));
+	BUG_ON(vif->pending_ring[pending_index(head)] != pending_idx);
 
 	do {
 		pending_ring_idx_t index;
 		pending_ring_idx_t idx = pending_index(head);
-		u16 info_idx = netbk->pending_ring[idx];
+		u16 info_idx = vif->pending_ring[idx];
 
-		pending_tx_info = &netbk->pending_tx_info[info_idx];
+		pending_tx_info = &vif->pending_tx_info[info_idx];
 		make_tx_response(vif, &pending_tx_info->req, status);
 
 		/* Setting any number other than
@@ -1664,18 +1482,15 @@ static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
 		 */
 		pending_tx_info->head = 0;
 
-		index = pending_index(netbk->pending_prod++);
-		netbk->pending_ring[index] = netbk->pending_ring[info_idx];
+		index = pending_index(vif->pending_prod++);
+		vif->pending_ring[index] = vif->pending_ring[info_idx];
 
-		xenvif_put(vif);
+		peek = vif->pending_ring[pending_index(++head)];
 
-		peek = netbk->pending_ring[pending_index(++head)];
+	} while (!pending_tx_is_head(vif, peek));
 
-	} while (!pending_tx_is_head(netbk, peek));
-
-	netbk->mmap_pages[pending_idx]->mapping = 0;
-	put_page(netbk->mmap_pages[pending_idx]);
-	netbk->mmap_pages[pending_idx] = NULL;
+	put_page(vif->mmap_pages[pending_idx]);
+	vif->mmap_pages[pending_idx] = NULL;
 }
 
 
@@ -1723,45 +1538,22 @@ static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
 	return resp;
 }
 
-static inline int rx_work_todo(struct xen_netbk *netbk)
+static inline int rx_work_todo(struct xenvif *vif)
 {
-	return !skb_queue_empty(&netbk->rx_queue);
+	return !skb_queue_empty(&vif->rx_queue);
 }
 
-static inline int tx_work_todo(struct xen_netbk *netbk)
+static inline int tx_work_todo(struct xenvif *vif)
 {
 
-	if ((nr_pending_reqs(netbk) + XEN_NETBK_LEGACY_SLOTS_MAX
-	     < MAX_PENDING_REQS) &&
-	     !list_empty(&netbk->net_schedule_list))
+	if (likely(RING_HAS_UNCONSUMED_REQUESTS(&vif->tx)) &&
+	    (nr_pending_reqs(vif) + XEN_NETBK_LEGACY_SLOTS_MAX
+	     < MAX_PENDING_REQS))
 		return 1;
 
 	return 0;
 }
 
-static int xen_netbk_kthread(void *data)
-{
-	struct xen_netbk *netbk = data;
-	while (!kthread_should_stop()) {
-		wait_event_interruptible(netbk->wq,
-				rx_work_todo(netbk) ||
-				tx_work_todo(netbk) ||
-				kthread_should_stop());
-		cond_resched();
-
-		if (kthread_should_stop())
-			break;
-
-		if (rx_work_todo(netbk))
-			xen_netbk_rx_action(netbk);
-
-		if (tx_work_todo(netbk))
-			xen_netbk_tx_action(netbk);
-	}
-
-	return 0;
-}
-
 void xen_netbk_unmap_frontend_rings(struct xenvif *vif)
 {
 	if (vif->tx.sring)
@@ -1807,11 +1599,29 @@ err:
 	return err;
 }
 
+int xen_netbk_kthread(void *data)
+{
+	struct xenvif *vif = data;
+
+	while (!kthread_should_stop()) {
+		wait_event_interruptible(vif->wq,
+					 rx_work_todo(vif) ||
+					 kthread_should_stop());
+		if (kthread_should_stop())
+			break;
+
+		if (rx_work_todo(vif))
+			xen_netbk_rx_action(vif);
+
+		cond_resched();
+	}
+
+	return 0;
+}
+
 static int __init netback_init(void)
 {
-	int i;
 	int rc = 0;
-	int group;
 
 	if (!xen_domain())
 		return -ENODEV;
@@ -1822,48 +1632,6 @@ static int __init netback_init(void)
 		fatal_skb_slots = XEN_NETBK_LEGACY_SLOTS_MAX;
 	}
 
-	xen_netbk_group_nr = num_online_cpus();
-	xen_netbk = vzalloc(sizeof(struct xen_netbk) * xen_netbk_group_nr);
-	if (!xen_netbk)
-		return -ENOMEM;
-
-	for (group = 0; group < xen_netbk_group_nr; group++) {
-		struct xen_netbk *netbk = &xen_netbk[group];
-		skb_queue_head_init(&netbk->rx_queue);
-		skb_queue_head_init(&netbk->tx_queue);
-
-		init_timer(&netbk->net_timer);
-		netbk->net_timer.data = (unsigned long)netbk;
-		netbk->net_timer.function = xen_netbk_alarm;
-
-		netbk->pending_cons = 0;
-		netbk->pending_prod = MAX_PENDING_REQS;
-		for (i = 0; i < MAX_PENDING_REQS; i++)
-			netbk->pending_ring[i] = i;
-
-		init_waitqueue_head(&netbk->wq);
-		netbk->task = kthread_create(xen_netbk_kthread,
-					     (void *)netbk,
-					     "netback/%u", group);
-
-		if (IS_ERR(netbk->task)) {
-			pr_alert("kthread_create() fails at netback\n");
-			del_timer(&netbk->net_timer);
-			rc = PTR_ERR(netbk->task);
-			goto failed_init;
-		}
-
-		kthread_bind(netbk->task, group);
-
-		INIT_LIST_HEAD(&netbk->net_schedule_list);
-
-		spin_lock_init(&netbk->net_schedule_list_lock);
-
-		atomic_set(&netbk->netfront_count, 0);
-
-		wake_up_process(netbk->task);
-	}
-
 	rc = xenvif_xenbus_init();
 	if (rc)
 		goto failed_init;
@@ -1871,35 +1639,14 @@ static int __init netback_init(void)
 	return 0;
 
 failed_init:
-	while (--group >= 0) {
-		struct xen_netbk *netbk = &xen_netbk[group];
-		del_timer(&netbk->net_timer);
-		kthread_stop(netbk->task);
-	}
-	vfree(xen_netbk);
 	return rc;
-
 }
 
 module_init(netback_init);
 
 static void __exit netback_fini(void)
 {
-	int i, j;
-
 	xenvif_xenbus_fini();
-
-	for (i = 0; i < xen_netbk_group_nr; i++) {
-		struct xen_netbk *netbk = &xen_netbk[i];
-		del_timer_sync(&netbk->net_timer);
-		kthread_stop(netbk->task);
-		for (j = 0; j < MAX_PENDING_REQS; j++) {
-			if (netbk->mmap_pages[j])
-				__free_page(netbk->mmap_pages[j]);
-		}
-	}
-
-	vfree(xen_netbk);
 }
 module_exit(netback_fini);