[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH v2] xen network backend driver
Ian Campbell <Ian.Campbell@xxxxxxxxxx> : [...] > * Dropped the tasklet mode for the backend worker leaving only the > kthread mode. I will revisit the suggestion to use NAPI on the > driver side in the future, I think it's somewhat orthogonal to > the use of kthread here, but it seems likely to be a worthwhile > improvement either way. I have not dug into bind_interdomain_evtchn_to_irqhandler but I would expect the kthread to go away once NAPI is plugged into xenvif_interrupt(). [...] > diff --git a/drivers/net/xen-netback/interface.c > b/drivers/net/xen-netback/interface.c > new file mode 100644 > index 0000000..98a992d > --- /dev/null > +++ b/drivers/net/xen-netback/interface.c > @@ -0,0 +1,550 @@ > +/* > + * Network-device interface management. > + * > + * Copyright (c) 2004-2005, Keir Fraser > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License version 2 > + * as published by the Free Software Foundation; or, when distributed > + * separately from the Linux kernel or incorporated into other > + * software packages, subject to the following license: > + * > + * Permission is hereby granted, free of charge, to any person obtaining a > copy > + * of this source file (the "Software"), to deal in the Software without > + * restriction, including without limitation the rights to use, copy, modify, > + * merge, publish, distribute, sublicense, and/or sell copies of the > Software, > + * and to permit persons to whom the Software is furnished to do so, subject > to > + * the following conditions: > + * > + * The above copyright notice and this permission notice shall be included in > + * all copies or substantial portions of the Software. > + * > + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR > + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, > + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL > THE > + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER > + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING > + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER > DEALINGS > + * IN THE SOFTWARE. > + */ > + > +#include "common.h" > + > +#include <linux/ethtool.h> > +#include <linux/rtnetlink.h> > + > +#include <xen/events.h> > +#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); > +} > + > +static int xenvif_max_required_rx_slots(struct xenvif *vif) > +{ > + int max = DIV_ROUND_UP(vif->dev->mtu, PAGE_SIZE); > + > + if (vif->can_sg || vif->gso || vif->gso_prefix) > + max += MAX_SKB_FRAGS + 1; /* extra_info + frags */ > + > + return max; > +} > + > +int xenvif_queue_full(struct xenvif *vif) > +{ > + RING_IDX peek = vif->rx_req_cons_peek; > + RING_IDX needed = xenvif_max_required_rx_slots(vif); > + > + return ((vif->rx.sring->req_prod - peek) < needed) || > + ((vif->rx.rsp_prod_pvt + XEN_NETIF_RX_RING_SIZE - peek) < > needed); > +} > + > +/* > + * Implement our own carrier flag: the network stack's version causes delays > + * when the carrier is re-enabled (in particular, dev_activate() may not > + * immediately be called, which can cause packet loss; also the etherbridge > + * can be rather lazy in activating its port). > + */ I have found a netif_carrier_off(vif->dev) but no netif_carrier_on(vif->dev). Did I overlook something ? > +static void xenvif_carrier_on(struct xenvif *vif) > +{ > + vif->carrier = 1; > +} > +static void xenvif_carrier_off(struct xenvif *vif) > +{ > + vif->carrier = 0; > +} > +static int xenvif_carrier_ok(struct xenvif *vif) > +{ > + return vif->carrier; > +} > + > +int xenvif_schedulable(struct xenvif *vif) > +{ > + return netif_running(vif->dev) && xenvif_carrier_ok(vif); > +} > + > +static irqreturn_t xenvif_interrupt(int irq, void *dev_id) > +{ > + struct xenvif *vif = dev_id; > + > + if (vif->netbk == NULL) > + return IRQ_NONE; > + > + xen_netbk_schedule_xenvif(vif); > + > + if (xenvif_schedulable(vif) && !xenvif_queue_full(vif)) This test appears three times along the code. Factor it out ? > + netif_wake_queue(vif->dev); > + > + return IRQ_HANDLED; > +} > + > +static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev) > +{ > + struct xenvif *vif = netdev_priv(dev); > + > + BUG_ON(skb->dev != dev); > + > + if (vif->netbk == NULL) How is it supposed to happen ? xenvif_open xenvif_up xen_netbk_add_xenvif netbk = &xen_netbk[min_group]; vif->netbk = netbk; netif_start_queue > + goto drop; > + > + /* Drop the packet if the target domain has no receive buffers. */ > + if (unlikely(!xenvif_schedulable(vif) || xenvif_queue_full(vif))) > + goto drop; > + > + /* 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 && xenvif_queue_full(vif)) { > + vif->rx.sring->req_event = vif->rx_req_cons_peek + > + xenvif_max_required_rx_slots(vif); > + mb(); /* request notification /then/ check & stop the queue */ > + if (xenvif_queue_full(vif)) > + netif_stop_queue(dev); > + } > + > + xen_netbk_queue_tx_skb(vif, skb); Why not do the real work (xen_netbk_rx_action) here and avoid the skb list lock ? Batching ? > + > + return 0; NETDEV_TX_OK > + > + drop: > + vif->stats.tx_dropped++; > + dev_kfree_skb(skb); > + return 0; NETDEV_TX_OK > +} > + [...] > +struct xenvif *xenvif_alloc(struct device *parent, domid_t domid, > + unsigned int handle) > +{ > + int err = 0; Useless init. > + struct net_device *dev; > + struct xenvif *vif; > + char name[IFNAMSIZ] = {}; > + > + snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle); > + dev = alloc_netdev(sizeof(struct xenvif), name, ether_setup); > + if (dev == NULL) { > + pr_debug("Could not allocate netdev\n"); > + return ERR_PTR(-ENOMEM); > + } > + > + SET_NETDEV_DEV(dev, parent); > + > + vif = netdev_priv(dev); > + memset(vif, 0, sizeof(*vif)); Useless memset. It is kzalloced behind the scene. > + 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->list); > + > + xenvif_carrier_off(vif); > + > + vif->credit_bytes = vif->remaining_credit = ~0UL; > + vif->credit_usec = 0UL; > + init_timer(&vif->credit_timeout); > + /* Initialize 'expires' now: it's used to track the credit window. */ > + vif->credit_timeout.expires = jiffies; > + > + dev->netdev_ops = &xenvif_netdev_ops; > + xenvif_set_features(vif); > + SET_ETHTOOL_OPS(dev, &xenvif_ethtool_ops); > + > + dev->tx_queue_len = XENVIF_QUEUE_LENGTH; > + > + /* > + * Initialise a dummy MAC address. We choose the numerically > + * largest non-broadcast address to prevent the address getting > + * stolen by an Ethernet bridge for STP purposes. > + * (FE:FF:FF:FF:FF:FF) > + */ > + memset(dev->dev_addr, 0xFF, ETH_ALEN); > + dev->dev_addr[0] &= ~0x01; > + > + rtnl_lock(); > + err = register_netdevice(dev); > + rtnl_unlock(); register_netdev() will do the locking for you. > + if (err) { > + pr_debug("Could not register new net device %s: err=%d\n", > + dev->name, err); > + free_netdev(dev); > + return ERR_PTR(err); > + } > + > + pr_debug("Successfully created xenvif\n"); > + return vif; > +} > + [...] > diff --git a/drivers/net/xen-netback/netback.c > b/drivers/net/xen-netback/netback.c > new file mode 100644 > index 0000000..fbddf3d > --- /dev/null > +++ b/drivers/net/xen-netback/netback.c [...] > +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]; > + struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS]; > + > + u16 pending_ring[MAX_PENDING_REQS]; Group the [MAX_PENDING_REQS] arrays as a single array ? > + > + /* > + * Each head or fragment can be up to 4096 bytes. Given > + * MAX_BUFFER_OFFSET of 4096 the worst case is that each > + * head/fragment uses 2 copy operation. > + */ > + struct gnttab_copy grant_copy_op[2*XEN_NETIF_RX_RING_SIZE]; > + unsigned char rx_notify[NR_IRQS]; > + u16 notify_list[XEN_NETIF_RX_RING_SIZE]; > + struct netbk_rx_meta meta[2*XEN_NETIF_RX_RING_SIZE]; > +}; > + [...] > +static int xen_netbk_kthread(void *data) > +{ > + struct xen_netbk *netbk = (struct xen_netbk *)data; Useless cast. > + while (!kthread_should_stop()) { > + wait_event_interruptible(netbk->wq, > + rx_work_todo(netbk) > + || tx_work_todo(netbk) > + || kthread_should_stop()); Please put || at the end of the line. [...] > +static int __init netback_init(void) > +{ > + int i; > + int rc = 0; > + int group; > + > + if (!xen_pv_domain()) > + return -ENODEV; > + > + xen_netbk_group_nr = num_online_cpus(); > + xen_netbk = vmalloc(sizeof(struct xen_netbk) * xen_netbk_group_nr); > + if (!xen_netbk) { > + printk(KERN_ALERT "%s: out of memory\n", __func__); > + return -ENOMEM; > + } > + memset(xen_netbk, 0, sizeof(struct xen_netbk) * xen_netbk_group_nr); vzalloc > + > + 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)) { > + printk(KERN_ALERT "kthread_run() 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; > + > + return 0; > + > +failed_init: > + for (i = 0; i < group; i++) { while (--group >= 0) ? > + struct xen_netbk *netbk = &xen_netbk[i]; > + int j; > + for (j = 0; j < MAX_PENDING_REQS; j++) { > + if (netbk->mmap_pages[i]) ^ j ? > + __free_page(netbk->mmap_pages[i]); ^ j ? > + } > + del_timer(&netbk->net_timer); > + kthread_stop(netbk->task); > + } > + vfree(xen_netbk); > + return rc; > + > +} > + -- Ueimor _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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