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Date: Mon, 4 Mar 2013 16:22:06 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Wei Liu <wei.liu2@...rix.com>
Cc: xen-devel@...ts.xen.org, netdev@...r.kernel.org,
ian.campbell@...rix.com, annie.li@...cle.com
Subject: Re: [PATCH 7/8] netback: split event channels support
On Fri, Feb 15, 2013 at 04:00:08PM +0000, Wei Liu wrote:
> Netback and netfront only use one event channel to do tx / rx notification.
> This may cause unnecessary wake-up of process routines. This patch adds a new
> feature called feautre-split-event-channel to netback, enabling it to handle
'feature', not 'feautre'. In the code it looks to also be plural:
feature-split-event-channels
and there is also event-channel-tx and event-channel-rx attribute.
You need to also send an patch to Xen hypervisor tree for this new XenBus
attributes and provide the appropiate syntax.
> Tx and Rx event separately.
>
> Netback will use tx_irq to notify guest for tx completion, rx_irq for rx
> notification.
>
> If frontend doesn't support this feature, tx_irq = rx_irq.
>
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> ---
> drivers/net/xen-netback/common.h | 10 +++--
> drivers/net/xen-netback/interface.c | 78 ++++++++++++++++++++++++++++-------
> drivers/net/xen-netback/netback.c | 7 ++--
> drivers/net/xen-netback/xenbus.c | 44 ++++++++++++++++----
> 4 files changed, 109 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index f541ba9..cc2a9f0 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -63,8 +63,11 @@ struct xenvif {
>
> u8 fe_dev_addr[6];
>
> - /* Physical parameters of the comms window. */
> - unsigned int irq;
> + /* Physical parameters of the comms window.
> + * When feature-split-event-channels = 0, tx_irq = rx_irq.
> + */
> + unsigned int tx_irq;
> + unsigned int rx_irq;
>
> /* List of frontends to notify after a batch of frames sent. */
> struct list_head notify_list;
> @@ -122,10 +125,11 @@ struct xenvif *xenvif_alloc(struct device *parent,
> domid_t domid,
> unsigned int handle);
>
> +/* When feature-split-event-channels == 0, tx_evtchn == rx_evtchn */
> int xenvif_connect(struct xenvif *vif,
> unsigned long *tx_ring_ref, unsigned int tx_ring_order,
> unsigned long *rx_ring_ref, unsigned int rx_ring_order,
> - unsigned int evtchn);
> + unsigned int tx_evtchn, unsigned int rx_evtchn);
> void xenvif_disconnect(struct xenvif *vif);
>
> void xenvif_get(struct xenvif *vif);
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index fa4d46d..c9ebe21 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -60,7 +60,8 @@ static int xenvif_rx_schedulable(struct xenvif *vif)
> return xenvif_schedulable(vif) && !xen_netbk_rx_ring_full(vif);
> }
>
> -static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
> +/* Tx interrupt handler used when feature-split-event-channels == 1 */
> +static irqreturn_t xenvif_tx_interrupt(int tx_irq, void *dev_id)
> {
> struct xenvif *vif = dev_id;
>
> @@ -69,12 +70,31 @@ static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
>
> xen_netbk_schedule_xenvif(vif);
>
> + return IRQ_HANDLED;
> +}
> +
> +/* Rx interrupt handler used when feature-split-event-channels == 1 */
> +static irqreturn_t xenvif_rx_interrupt(int rx_irq, void *dev_id)
> +{
> + struct xenvif *vif = dev_id;
> +
> + if (vif->netbk == NULL)
> + return IRQ_NONE;
> +
> if (xenvif_rx_schedulable(vif))
> netif_wake_queue(vif->dev);
>
> return IRQ_HANDLED;
> }
>
> +/* Used when feature-split-event-channels == 0 */
> +static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
> +{
> + xenvif_tx_interrupt(irq, dev_id);
> + xenvif_rx_interrupt(irq, dev_id);
> + return IRQ_HANDLED;
> +}
> +
> static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
> {
> struct xenvif *vif = netdev_priv(dev);
> @@ -125,13 +145,15 @@ static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
> static void xenvif_up(struct xenvif *vif)
> {
> xen_netbk_add_xenvif(vif);
> - enable_irq(vif->irq);
> + enable_irq(vif->tx_irq);
> + enable_irq(vif->rx_irq);
> xen_netbk_check_rx_xenvif(vif);
> }
>
> static void xenvif_down(struct xenvif *vif)
> {
> - disable_irq(vif->irq);
> + disable_irq(vif->tx_irq);
> + disable_irq(vif->rx_irq);
> del_timer_sync(&vif->credit_timeout);
> xen_netbk_deschedule_xenvif(vif);
> xen_netbk_remove_xenvif(vif);
> @@ -308,7 +330,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
> int xenvif_connect(struct xenvif *vif,
> unsigned long *tx_ring_ref, unsigned int tx_ring_ref_count,
> unsigned long *rx_ring_ref, unsigned int rx_ring_ref_count,
> - unsigned int evtchn)
> + unsigned int tx_evtchn, unsigned int rx_evtchn)
> {
> int err = -ENOMEM;
> void *addr;
> @@ -317,7 +339,7 @@ int xenvif_connect(struct xenvif *vif,
> int tmp[NETBK_MAX_RING_PAGES], i;
>
> /* Already connected through? */
> - if (vif->irq)
> + if (vif->tx_irq)
> return 0;
>
> __module_get(THIS_MODULE);
> @@ -347,13 +369,32 @@ int xenvif_connect(struct xenvif *vif,
> BACK_RING_INIT(&vif->rx, rxs, PAGE_SIZE * rx_ring_ref_count);
> vif->nr_rx_handles = rx_ring_ref_count;
>
> - err = bind_interdomain_evtchn_to_irqhandler(
> - vif->domid, evtchn, xenvif_interrupt, 0,
> - vif->dev->name, vif);
> - if (err < 0)
> - goto err_rx_unmap;
> - vif->irq = err;
> - disable_irq(vif->irq);
> + if (tx_evtchn == rx_evtchn) { /* feature-split-event-channels == 0 */
> + err = bind_interdomain_evtchn_to_irqhandler(
> + vif->domid, tx_evtchn, xenvif_interrupt, 0,
> + vif->dev->name, vif);
> + if (err < 0)
> + goto err_rx_unmap;
> + vif->tx_irq = vif->rx_irq = err;
> + disable_irq(vif->tx_irq);
> + disable_irq(vif->rx_irq);
> + } else { /* feature-split-event-channels == 1 */
> + err = bind_interdomain_evtchn_to_irqhandler(
> + vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
> + vif->dev->name, vif);
> + if (err < 0)
> + goto err_rx_unmap;
> + vif->tx_irq = err;
> + disable_irq(vif->tx_irq);
> +
> + err = bind_interdomain_evtchn_to_irqhandler(
> + vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
> + vif->dev->name, vif);
> + if (err < 0)
> + goto err_tx_unbind;
> + vif->rx_irq = err;
> + disable_irq(vif->rx_irq);
> + }
>
> xenvif_get(vif);
>
> @@ -367,6 +408,10 @@ int xenvif_connect(struct xenvif *vif,
> rtnl_unlock();
>
> return 0;
> +
> +err_tx_unbind:
> + unbind_from_irqhandler(vif->tx_irq, vif);
> + vif->tx_irq = 0;
> err_rx_unmap:
> xen_netbk_unmap_frontend_rings(vif, (void *)vif->rx.sring);
> vif->nr_rx_handles = 0;
> @@ -406,8 +451,13 @@ void xenvif_disconnect(struct xenvif *vif)
> atomic_dec(&vif->refcnt);
> wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
>
> - if (vif->irq) {
> - unbind_from_irqhandler(vif->irq, vif);
> + if (vif->tx_irq) {
> + if (vif->tx_irq == vif->rx_irq)
> + unbind_from_irqhandler(vif->tx_irq, vif);
> + else {
> + unbind_from_irqhandler(vif->tx_irq, vif);
> + unbind_from_irqhandler(vif->rx_irq, vif);
> + }
> need_module_put = 1;
> }
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 644c760..5ac8c35 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -639,7 +639,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
> {
> struct xenvif *vif = NULL, *tmp;
> s8 status;
> - u16 irq, flags;
> + u16 flags;
> struct xen_netif_rx_response *resp;
> struct sk_buff_head rxq;
> struct sk_buff *skb;
> @@ -750,7 +750,6 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
> sco->meta_slots_used);
>
> RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->rx, ret);
> - irq = vif->irq;
> if (ret && list_empty(&vif->notify_list))
> list_add_tail(&vif->notify_list, ¬ify);
>
> @@ -762,7 +761,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
> }
>
> list_for_each_entry_safe(vif, tmp, ¬ify, notify_list) {
> - notify_remote_via_irq(vif->irq);
> + notify_remote_via_irq(vif->rx_irq);
> list_del_init(&vif->notify_list);
> }
>
> @@ -1595,7 +1594,7 @@ static void make_tx_response(struct xenvif *vif,
> vif->tx.rsp_prod_pvt = ++i;
> RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&vif->tx, notify);
> if (notify)
> - notify_remote_via_irq(vif->irq);
> + notify_remote_via_irq(vif->tx_irq);
> }
>
> static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif,
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> index 1791807..6822d89 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -141,6 +141,15 @@ static int netback_probe(struct xenbus_device *dev,
> goto abort_transaction;
> }
>
> + /* Split event channels support */
> + err = xenbus_printf(xbt, dev->nodename,
> + "feature-split-event-channels",
> + "%u", 1);
> + if (err) {
> + message = "writing feature-split-event-channels";
> + goto abort_transaction;
> + }
I wouldn't abort b/c of it. Just continue on without using this.
> +
> err = xenbus_transaction_end(xbt, 0);
> } while (err == -EAGAIN);
>
> @@ -419,7 +428,7 @@ static int connect_rings(struct backend_info *be)
> {
> struct xenvif *vif = be->vif;
> struct xenbus_device *dev = be->dev;
> - unsigned int evtchn, rx_copy;
> + unsigned int tx_evtchn, rx_evtchn, rx_copy;
> int err;
> int val;
> unsigned long tx_ring_ref[NETBK_MAX_RING_PAGES];
> @@ -428,12 +437,22 @@ static int connect_rings(struct backend_info *be)
> unsigned int rx_ring_order;
>
> err = xenbus_gather(XBT_NIL, dev->otherend,
> - "event-channel", "%u", &evtchn, NULL);
> + "event-channel", "%u", &tx_evtchn, NULL);
> if (err) {
> - xenbus_dev_fatal(dev, err,
> - "reading %s/event-channel",
> - dev->otherend);
> - return err;
> + /* try split event channels */
> + err = xenbus_gather(XBT_NIL, dev->otherend,
> + "event-channel-tx", "%u", &tx_evtchn,
> + "event-channel-rx", "%u", &rx_evtchn,
> + NULL);
> + if (err) {
> + xenbus_dev_fatal(dev, err,
> + "reading %s/event-channel(-tx/rx)",
> + dev->otherend);
> + return err;
> + }
> + } else { /* frontend doesn't support split event channels */
> + rx_evtchn = tx_evtchn;
> + dev_info(&dev->dev, "single event channel\n");
> }
>
> err = xenbus_scanf(XBT_NIL, dev->otherend, "tx-ring-order", "%u",
> @@ -568,12 +587,19 @@ static int connect_rings(struct backend_info *be)
> /* Map the shared frame, irq etc. */
> err = xenvif_connect(vif, tx_ring_ref, (1U << tx_ring_order),
> rx_ring_ref, (1U << rx_ring_order),
> - evtchn);
> + tx_evtchn, rx_evtchn);
> if (err) {
> /* construct 1 2 3 / 4 5 6 */
> int i;
> char txs[3 * (1U << MODPARM_netback_max_tx_ring_page_order)];
> char rxs[3 * (1U << MODPARM_netback_max_rx_ring_page_order)];
> + char evtchns[20];
> +
> + if (tx_evtchn == rx_evtchn)
> + snprintf(evtchns, sizeof(evtchns)-1, "%u", tx_evtchn);
> + else
> + snprintf(evtchns, sizeof(evtchns)-1, "%u/%u",
> + tx_evtchn, rx_evtchn);
>
> txs[0] = rxs[0] = 0;
>
> @@ -586,8 +612,8 @@ static int connect_rings(struct backend_info *be)
> " %lu", rx_ring_ref[i]);
>
> xenbus_dev_fatal(dev, err,
> - "mapping shared-frames%s /%s port %u",
> - txs, rxs, evtchn);
> + "mapping shared-frames%s /%s port %s",
> + txs, rxs, evtchns);
> return err;
> }
> return 0;
> --
> 1.7.10.4
>
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