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>
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 087d2db..44d6b70 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -30,6 +30,7 @@
#include "common.h"
+#include <linux/kthread.h>
#include <linux/ethtool.h>
#include <linux/rtnetlink.h>
#include <linux/if_vlan.h>
@@ -38,17 +39,7 @@
#include <asm/xen/hypercall.h>
#define XENVIF_QUEUE_LENGTH 32
-
-void xenvif_get(struct xenvif *vif)
-{
- atomic_inc(&vif->refcnt);
-}
-
-void xenvif_put(struct xenvif *vif)
-{
- if (atomic_dec_and_test(&vif->refcnt))
- wake_up(&vif->waiting_to_free);
-}
+#define XENVIF_NAPI_WEIGHT 64
int xenvif_schedulable(struct xenvif *vif)
{
@@ -64,21 +55,55 @@
{
struct xenvif *vif = dev_id;
- if (vif->netbk == NULL)
- return IRQ_HANDLED;
-
- xen_netbk_schedule_xenvif(vif);
+ if (RING_HAS_UNCONSUMED_REQUESTS(&vif->tx))
+ napi_schedule(&vif->napi);
return IRQ_HANDLED;
}
+static int xenvif_poll(struct napi_struct *napi, int budget)
+{
+ struct xenvif *vif = container_of(napi, struct xenvif, napi);
+ int work_done;
+
+ work_done = xen_netbk_tx_action(vif, budget);
+
+ if (work_done < budget) {
+ int more_to_do = 0;
+ unsigned long flags;
+
+ /* It is necessary to disable IRQ before calling
+ * RING_HAS_UNCONSUMED_REQUESTS. Otherwise we might
+ * lose event from the frontend.
+ *
+ * Consider:
+ * RING_HAS_UNCONSUMED_REQUESTS
+ * <frontend generates event to trigger napi_schedule>
+ * __napi_complete
+ *
+ * This handler is still in scheduled state so the
+ * event has no effect at all. After __napi_complete
+ * this handler is descheduled and cannot get
+ * scheduled again. We lose event in this case and the ring
+ * will be completely stalled.
+ */
+
+ local_irq_save(flags);
+
+ RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, more_to_do);
+ if (!more_to_do)
+ __napi_complete(napi);
+
+ local_irq_restore(flags);
+ }
+
+ return work_done;
+}
+
static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
{
struct xenvif *vif = dev_id;
- if (vif->netbk == NULL)
- return IRQ_HANDLED;
-
if (xenvif_rx_schedulable(vif))
netif_wake_queue(vif->dev);
@@ -99,7 +124,8 @@
BUG_ON(skb->dev != dev);
- if (vif->netbk == NULL)
+ /* Drop the packet if vif is not ready */
+ if (vif->task == NULL)
goto drop;
/* Drop the packet if the target domain has no receive buffers. */
@@ -108,7 +134,6 @@
/* Reserve ring slots for the worst-case number of fragments. */
vif->rx_req_cons_peek += xen_netbk_count_skb_slots(vif, skb);
- xenvif_get(vif);
if (vif->can_queue && xen_netbk_must_stop_queue(vif))
netif_stop_queue(dev);
@@ -123,11 +148,6 @@
return NETDEV_TX_OK;
}
-void xenvif_receive_skb(struct xenvif *vif, struct sk_buff *skb)
-{
- netif_rx_ni(skb);
-}
-
void xenvif_notify_tx_completion(struct xenvif *vif)
{
if (netif_queue_stopped(vif->dev) && xenvif_rx_schedulable(vif))
@@ -142,7 +162,7 @@
static void xenvif_up(struct xenvif *vif)
{
- xen_netbk_add_xenvif(vif);
+ napi_enable(&vif->napi);
enable_irq(vif->tx_irq);
if (vif->tx_irq != vif->rx_irq)
enable_irq(vif->rx_irq);
@@ -151,12 +171,11 @@
static void xenvif_down(struct xenvif *vif)
{
+ napi_disable(&vif->napi);
disable_irq(vif->tx_irq);
if (vif->tx_irq != vif->rx_irq)
disable_irq(vif->rx_irq);
del_timer_sync(&vif->credit_timeout);
- xen_netbk_deschedule_xenvif(vif);
- xen_netbk_remove_xenvif(vif);
}
static int xenvif_open(struct net_device *dev)
@@ -272,11 +291,12 @@
struct net_device *dev;
struct xenvif *vif;
char name[IFNAMSIZ] = {};
+ int i;
snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
dev = alloc_netdev(sizeof(struct xenvif), name, ether_setup);
if (dev == NULL) {
- pr_warn("Could not allocate netdev\n");
+ pr_warn("Could not allocate netdev for %s\n", name);
return ERR_PTR(-ENOMEM);
}
@@ -285,14 +305,9 @@
vif = netdev_priv(dev);
vif->domid = domid;
vif->handle = handle;
- vif->netbk = NULL;
vif->can_sg = 1;
vif->csum = 1;
- atomic_set(&vif->refcnt, 1);
- init_waitqueue_head(&vif->waiting_to_free);
vif->dev = dev;
- INIT_LIST_HEAD(&vif->schedule_list);
- INIT_LIST_HEAD(&vif->notify_list);
vif->credit_bytes = vif->remaining_credit = ~0UL;
vif->credit_usec = 0UL;
@@ -307,6 +322,16 @@
dev->tx_queue_len = XENVIF_QUEUE_LENGTH;
+ skb_queue_head_init(&vif->rx_queue);
+ skb_queue_head_init(&vif->tx_queue);
+
+ vif->pending_cons = 0;
+ vif->pending_prod = MAX_PENDING_REQS;
+ for (i = 0; i < MAX_PENDING_REQS; i++)
+ vif->pending_ring[i] = i;
+ for (i = 0; i < MAX_PENDING_REQS; i++)
+ vif->mmap_pages[i] = NULL;
+
/*
* Initialise a dummy MAC address. We choose the numerically
* largest non-broadcast address to prevent the address getting
@@ -316,6 +341,8 @@
memset(dev->dev_addr, 0xFF, ETH_ALEN);
dev->dev_addr[0] &= ~0x01;
+ netif_napi_add(dev, &vif->napi, xenvif_poll, XENVIF_NAPI_WEIGHT);
+
netif_carrier_off(dev);
err = register_netdev(dev);
@@ -377,7 +404,14 @@
disable_irq(vif->rx_irq);
}
- xenvif_get(vif);
+ init_waitqueue_head(&vif->wq);
+ vif->task = kthread_create(xen_netbk_kthread,
+ (void *)vif, vif->dev->name);
+ if (IS_ERR(vif->task)) {
+ pr_warn("Could not allocate kthread for %s\n", vif->dev->name);
+ err = PTR_ERR(vif->task);
+ goto err_rx_unbind;
+ }
rtnl_lock();
if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
@@ -388,7 +422,13 @@
xenvif_up(vif);
rtnl_unlock();
+ wake_up_process(vif->task);
+
return 0;
+
+err_rx_unbind:
+ unbind_from_irqhandler(vif->rx_irq, vif);
+ vif->rx_irq = 0;
err_tx_unbind:
unbind_from_irqhandler(vif->tx_irq, vif);
vif->tx_irq = 0;
@@ -408,7 +448,6 @@
if (netif_running(dev))
xenvif_down(vif);
rtnl_unlock();
- xenvif_put(vif);
}
void xenvif_disconnect(struct xenvif *vif)
@@ -422,9 +461,6 @@
if (netif_carrier_ok(vif->dev))
xenvif_carrier_off(vif);
- atomic_dec(&vif->refcnt);
- wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
-
if (vif->tx_irq) {
if (vif->tx_irq == vif->rx_irq)
unbind_from_irqhandler(vif->tx_irq, vif);
@@ -438,6 +474,11 @@
need_module_put = 1;
}
+ if (vif->task)
+ kthread_stop(vif->task);
+
+ netif_napi_del(&vif->napi);
+
unregister_netdev(vif->dev);
xen_netbk_unmap_frontend_rings(vif);