[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH V2] xen/netfront: handle compound page fragments on transmit
On Tue, 2012-11-20 at 16:00 +0000, Ian Campbell wrote: > An SKB paged fragment can consist of a compound page with order > 0. > However the netchannel protocol deals only in PAGE_SIZE frames. > > Handle this in xennet_make_frags by iterating over the frames which > make up the page. > > This is the netfront equivalent to 6a8ed462f16b for netback. ... > - frags += DIV_ROUND_UP(offset + len, PAGE_SIZE); > - if (unlikely(frags > MAX_SKB_FRAGS + 1)) { > - printk(KERN_ALERT "xennet: skb rides the rocket: %d frags\n", > - frags); > - dump_stack(); > + slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) + > + xennet_count_skb_frag_slots(skb); > + if (unlikely(slots > MAX_SKB_FRAGS + 1)) { > + printk(KERN_ALERT "xennet: skb rides the rocket: %d slots\n", > + slots); I think this is wrong. You should change netfront_tx_slot_available() to stop the queue before this can happen. Yes, you dont hit this on your tests, but a driver should not drop a good packet. > goto drop; > } > > spin_lock_irqsave(&np->tx_lock, flags); > > if (unlikely(!netif_carrier_ok(dev) || > - (frags > 1 && !xennet_can_sg(dev)) || > + (slots > 1 && !xennet_can_sg(dev)) || > netif_needs_gso(skb, netif_skb_features(skb)))) { > spin_unlock_irqrestore(&np->tx_lock, flags); > goto drop; diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index caa0110..cb1e605 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -215,10 +215,13 @@ static void rx_refill_timeout(unsigned long data) napi_schedule(&np->napi); } +/* Considering a 64Kb packet of 16 frags, each frag can be mapped + * to 3 order-0 parts on pathological cases + */ static int netfront_tx_slot_available(struct netfront_info *np) { return (np->tx.req_prod_pvt - np->tx.rsp_cons) < - (TX_MAX_TARGET - MAX_SKB_FRAGS - 2); + (TX_MAX_TARGET - 3*MAX_SKB_FRAGS - 2); } static void xennet_maybe_wake_tx(struct net_device *dev) _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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