Merge branch 'xen-netback-next'
Zoltan Kiss says: ==================== xen-netback: Changes around carrier handling This series starts using carrier off as a way to purge packets when the guest is not able (or willing) to receive them. It is a much faster way to get rid of packets waiting for an overwhelmed guest. The first patch changes current netback code where it relies currently on netif_carrier_ok. The second turns off the carrier if the guest times out on a queue, and only turn it on again if that queue (or queues) resurrects. ==================== Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller
commit
61675fea33
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@ -176,9 +176,9 @@ struct xenvif_queue { /* Per-queue data for xenvif */
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struct xen_netif_rx_back_ring rx;
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struct sk_buff_head rx_queue;
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RING_IDX rx_last_skb_slots;
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bool rx_queue_purge;
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unsigned long status;
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struct timer_list wake_queue;
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struct timer_list rx_stalled;
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struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];
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@ -198,6 +198,20 @@ struct xenvif_queue { /* Per-queue data for xenvif */
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struct xenvif_stats stats;
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};
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enum state_bit_shift {
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/* This bit marks that the vif is connected */
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VIF_STATUS_CONNECTED,
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/* This bit signals the RX thread that queuing was stopped (in
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* start_xmit), and either the timer fired or an RX interrupt came
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*/
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QUEUE_STATUS_RX_PURGE_EVENT,
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/* This bit tells the interrupt handler that this queue was the reason
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* for the carrier off, so it should kick the thread. Only queues which
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* brought it down can turn on the carrier.
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*/
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QUEUE_STATUS_RX_STALLED
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};
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struct xenvif {
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/* Unique identifier for this interface. */
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domid_t domid;
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@ -220,6 +234,7 @@ struct xenvif {
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* frontend is rogue.
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*/
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bool disabled;
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unsigned long status;
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/* Queues */
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struct xenvif_queue *queues;
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@ -55,7 +55,8 @@ static inline void xenvif_stop_queue(struct xenvif_queue *queue)
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int xenvif_schedulable(struct xenvif *vif)
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{
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return netif_running(vif->dev) && netif_carrier_ok(vif->dev);
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return netif_running(vif->dev) &&
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test_bit(VIF_STATUS_CONNECTED, &vif->status);
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}
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static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
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@ -77,8 +78,12 @@ int xenvif_poll(struct napi_struct *napi, int budget)
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/* This vif is rogue, we pretend we've there is nothing to do
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* for this vif to deschedule it from NAPI. But this interface
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* will be turned off in thread context later.
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* Also, if a guest doesn't post enough slots to receive data on one of
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* its queues, the carrier goes down and NAPI is descheduled here so
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* the guest can't send more packets until it's ready to receive.
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*/
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if (unlikely(queue->vif->disabled)) {
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if (unlikely(queue->vif->disabled ||
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!netif_carrier_ok(queue->vif->dev))) {
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napi_complete(napi);
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return 0;
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}
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@ -96,7 +101,16 @@ int xenvif_poll(struct napi_struct *napi, int budget)
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static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
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{
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struct xenvif_queue *queue = dev_id;
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struct netdev_queue *net_queue =
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netdev_get_tx_queue(queue->vif->dev, queue->id);
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/* QUEUE_STATUS_RX_PURGE_EVENT is only set if either QDisc was off OR
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* the carrier went down and this queue was previously blocked
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*/
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if (unlikely(netif_tx_queue_stopped(net_queue) ||
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(!netif_carrier_ok(queue->vif->dev) &&
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test_bit(QUEUE_STATUS_RX_STALLED, &queue->status))))
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set_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status);
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xenvif_kick_thread(queue);
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return IRQ_HANDLED;
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@ -124,16 +138,14 @@ void xenvif_wake_queue(struct xenvif_queue *queue)
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netif_tx_wake_queue(netdev_get_tx_queue(dev, id));
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}
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/* Callback to wake the queue and drain it on timeout */
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static void xenvif_wake_queue_callback(unsigned long data)
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/* Callback to wake the queue's thread and turn the carrier off on timeout */
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static void xenvif_rx_stalled(unsigned long data)
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{
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struct xenvif_queue *queue = (struct xenvif_queue *)data;
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if (xenvif_queue_stopped(queue)) {
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netdev_err(queue->vif->dev, "draining TX queue\n");
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queue->rx_queue_purge = true;
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set_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status);
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xenvif_kick_thread(queue);
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xenvif_wake_queue(queue);
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}
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}
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@ -182,11 +194,11 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
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* drain.
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*/
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if (!xenvif_rx_ring_slots_available(queue, min_slots_needed)) {
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queue->wake_queue.function = xenvif_wake_queue_callback;
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queue->wake_queue.data = (unsigned long)queue;
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queue->rx_stalled.function = xenvif_rx_stalled;
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queue->rx_stalled.data = (unsigned long)queue;
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xenvif_stop_queue(queue);
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mod_timer(&queue->wake_queue,
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jiffies + rx_drain_timeout_jiffies);
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mod_timer(&queue->rx_stalled,
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jiffies + rx_drain_timeout_jiffies);
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}
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skb_queue_tail(&queue->rx_queue, skb);
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@ -267,7 +279,7 @@ static void xenvif_down(struct xenvif *vif)
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static int xenvif_open(struct net_device *dev)
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{
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struct xenvif *vif = netdev_priv(dev);
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if (netif_carrier_ok(dev))
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if (test_bit(VIF_STATUS_CONNECTED, &vif->status))
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xenvif_up(vif);
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netif_tx_start_all_queues(dev);
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return 0;
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@ -276,7 +288,7 @@ static int xenvif_open(struct net_device *dev)
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static int xenvif_close(struct net_device *dev)
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{
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struct xenvif *vif = netdev_priv(dev);
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if (netif_carrier_ok(dev))
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if (test_bit(VIF_STATUS_CONNECTED, &vif->status))
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xenvif_down(vif);
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netif_tx_stop_all_queues(dev);
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return 0;
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@ -514,7 +526,7 @@ int xenvif_init_queue(struct xenvif_queue *queue)
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queue->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
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}
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init_timer(&queue->wake_queue);
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init_timer(&queue->rx_stalled);
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netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
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XENVIF_NAPI_WEIGHT);
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@ -528,6 +540,7 @@ void xenvif_carrier_on(struct xenvif *vif)
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if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
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dev_set_mtu(vif->dev, ETH_DATA_LEN);
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netdev_update_features(vif->dev);
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set_bit(VIF_STATUS_CONNECTED, &vif->status);
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netif_carrier_on(vif->dev);
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if (netif_running(vif->dev))
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xenvif_up(vif);
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@ -625,9 +638,11 @@ void xenvif_carrier_off(struct xenvif *vif)
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struct net_device *dev = vif->dev;
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rtnl_lock();
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netif_carrier_off(dev); /* discard queued packets */
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if (netif_running(dev))
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xenvif_down(vif);
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if (test_and_clear_bit(VIF_STATUS_CONNECTED, &vif->status)) {
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netif_carrier_off(dev); /* discard queued packets */
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if (netif_running(dev))
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xenvif_down(vif);
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}
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rtnl_unlock();
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}
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@ -656,14 +671,13 @@ void xenvif_disconnect(struct xenvif *vif)
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unsigned int num_queues = vif->num_queues;
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unsigned int queue_index;
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if (netif_carrier_ok(vif->dev))
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xenvif_carrier_off(vif);
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xenvif_carrier_off(vif);
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for (queue_index = 0; queue_index < num_queues; ++queue_index) {
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queue = &vif->queues[queue_index];
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if (queue->task) {
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del_timer_sync(&queue->wake_queue);
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del_timer_sync(&queue->rx_stalled);
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kthread_stop(queue->task);
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queue->task = NULL;
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}
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@ -705,16 +719,12 @@ void xenvif_free(struct xenvif *vif)
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/* Here we want to avoid timeout messages if an skb can be legitimately
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* stuck somewhere else. Realistically this could be an another vif's
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* internal or QDisc queue. That another vif also has this
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* rx_drain_timeout_msecs timeout, but the timer only ditches the
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* internal queue. After that, the QDisc queue can put in worst case
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* XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS skbs into that another vif's
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* internal queue, so we need several rounds of such timeouts until we
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* can be sure that no another vif should have skb's from us. We are
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* not sending more skb's, so newly stuck packets are not interesting
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* for us here.
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* rx_drain_timeout_msecs timeout, so give it time to drain out.
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* Although if that other guest wakes up just before its timeout happens
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* and takes only one skb from QDisc, it can hold onto other skbs for a
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* longer period.
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*/
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unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000) *
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DIV_ROUND_UP(XENVIF_QUEUE_LENGTH, (XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS));
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unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000);
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unregister_netdev(vif->dev);
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@ -1869,8 +1869,7 @@ void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx)
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static inline int rx_work_todo(struct xenvif_queue *queue)
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{
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return (!skb_queue_empty(&queue->rx_queue) &&
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xenvif_rx_ring_slots_available(queue, queue->rx_last_skb_slots)) ||
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queue->rx_queue_purge;
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xenvif_rx_ring_slots_available(queue, queue->rx_last_skb_slots));
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}
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static inline int tx_work_todo(struct xenvif_queue *queue)
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@ -1935,6 +1934,75 @@ static void xenvif_start_queue(struct xenvif_queue *queue)
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xenvif_wake_queue(queue);
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}
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/* Only called from the queue's thread, it handles the situation when the guest
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* doesn't post enough requests on the receiving ring.
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* First xenvif_start_xmit disables QDisc and start a timer, and then either the
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* timer fires, or the guest send an interrupt after posting new request. If it
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* is the timer, the carrier is turned off here.
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* */
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static void xenvif_rx_purge_event(struct xenvif_queue *queue)
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{
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/* Either the last unsuccesful skb or at least 1 slot should fit */
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int needed = queue->rx_last_skb_slots ?
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queue->rx_last_skb_slots : 1;
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/* It is assumed that if the guest post new slots after this, the RX
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* interrupt will set the QUEUE_STATUS_RX_PURGE_EVENT bit and wake up
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* the thread again
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*/
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set_bit(QUEUE_STATUS_RX_STALLED, &queue->status);
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if (!xenvif_rx_ring_slots_available(queue, needed)) {
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rtnl_lock();
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if (netif_carrier_ok(queue->vif->dev)) {
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/* Timer fired and there are still no slots. Turn off
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* everything except the interrupts
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*/
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netif_carrier_off(queue->vif->dev);
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skb_queue_purge(&queue->rx_queue);
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queue->rx_last_skb_slots = 0;
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if (net_ratelimit())
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netdev_err(queue->vif->dev, "Carrier off due to lack of guest response on queue %d\n", queue->id);
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} else {
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/* Probably an another queue already turned the carrier
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* off, make sure nothing is stucked in the internal
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* queue of this queue
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*/
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skb_queue_purge(&queue->rx_queue);
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queue->rx_last_skb_slots = 0;
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}
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rtnl_unlock();
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} else if (!netif_carrier_ok(queue->vif->dev)) {
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unsigned int num_queues = queue->vif->num_queues;
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unsigned int i;
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/* The carrier was down, but an interrupt kicked
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* the thread again after new requests were
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* posted
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*/
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clear_bit(QUEUE_STATUS_RX_STALLED,
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&queue->status);
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rtnl_lock();
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netif_carrier_on(queue->vif->dev);
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netif_tx_wake_all_queues(queue->vif->dev);
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rtnl_unlock();
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for (i = 0; i < num_queues; i++) {
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struct xenvif_queue *temp = &queue->vif->queues[i];
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xenvif_napi_schedule_or_enable_events(temp);
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}
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if (net_ratelimit())
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netdev_err(queue->vif->dev, "Carrier on again\n");
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} else {
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/* Queuing were stopped, but the guest posted
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* new requests and sent an interrupt
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*/
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clear_bit(QUEUE_STATUS_RX_STALLED,
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&queue->status);
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del_timer_sync(&queue->rx_stalled);
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xenvif_start_queue(queue);
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}
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}
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int xenvif_kthread_guest_rx(void *data)
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{
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struct xenvif_queue *queue = data;
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@ -1944,8 +2012,12 @@ int xenvif_kthread_guest_rx(void *data)
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wait_event_interruptible(queue->wq,
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rx_work_todo(queue) ||
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queue->vif->disabled ||
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test_bit(QUEUE_STATUS_RX_PURGE_EVENT, &queue->status) ||
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kthread_should_stop());
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if (kthread_should_stop())
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break;
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/* This frontend is found to be rogue, disable it in
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* kthread context. Currently this is only set when
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* netback finds out frontend sends malformed packet,
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@ -1953,26 +2025,23 @@ int xenvif_kthread_guest_rx(void *data)
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* context so we defer it here, if this thread is
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* associated with queue 0.
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*/
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if (unlikely(queue->vif->disabled && netif_carrier_ok(queue->vif->dev) && queue->id == 0))
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if (unlikely(queue->vif->disabled && queue->id == 0))
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xenvif_carrier_off(queue->vif);
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if (kthread_should_stop())
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break;
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if (queue->rx_queue_purge) {
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else if (unlikely(test_and_clear_bit(QUEUE_STATUS_RX_PURGE_EVENT,
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&queue->status))) {
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xenvif_rx_purge_event(queue);
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} else if (!netif_carrier_ok(queue->vif->dev)) {
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/* Another queue stalled and turned the carrier off, so
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* purge the internal queue of queues which were not
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* blocked
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*/
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skb_queue_purge(&queue->rx_queue);
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queue->rx_queue_purge = false;
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queue->rx_last_skb_slots = 0;
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}
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if (!skb_queue_empty(&queue->rx_queue))
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xenvif_rx_action(queue);
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if (skb_queue_empty(&queue->rx_queue) &&
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xenvif_queue_stopped(queue)) {
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del_timer_sync(&queue->wake_queue);
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xenvif_start_queue(queue);
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}
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cond_resched();
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}
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Reference in a new issue