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Re: [Xen-devel] xennet: skb rides the rocket: 20 slots

To: Ian Campbell <Ian.Campbell@xxxxxxxxxx>

From: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>

Date: Mon, 7 Jan 2013 13:30:29 +0100

Cc: ANNIE LI <annie.li@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxx>

Delivery-date: Mon, 07 Jan 2013 12:30:55 +0000

List-id: Xen developer discussion <xen-devel.lists.xen.org>

Monday, January 7, 2013, 11:55:15 AM, you wrote: > On Fri, 2013-01-04 at 16:28 +0000, Sander Eikelenboom wrote: >> Hi Ian, > I'm not actually the netfront maintainer. Adding Konrad. Annie too since > IIRC she was at one point looking at various buffer coalescing schemes. Ah ok, i thought you were :-) sorry >> Today i fired up an old VM with a bittorrent client, trying to >> download some torrents. > How old? Which kernel? 3.8.0-rc2 at the moment, it's a PV guest. >> I seem to be hitting the unlikely case of "xennet: skb rides the >> rocket: xx slots" and this results in some dropped packets in domU, I >> don't see any warnings in dom0. >> >> I have added some extra info, but i don't have enough knowledge if >> this could/should be prevented from happening ? > MAX_SKB_FRAGS has never, AFAIK, been as big as 19 or 20 so I'm not sure > this can have ever worked. > These SKBs seem to be pretty big (not quite 64KB), seemingly most of the > data is contained in a smallish number of frags, which suggests compound > pages and therefore a reasonably modern kernel? > This probably relates somewhat to the issues described in the > "netchannel vs MAX_SKB_FRAGS" thread last year, or at least the solution > to that would necessarily involve fixing this issue. > In the meantime you could try disabling sg and/or various offloads for > that domain's vif. Will do. >> [16798.629141] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16800.575182] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16801.589166] xennet: skb rides the rocket: 20 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:19 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:5 >> page_size:4096 prot:0800 >> [16803.279039] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:3 >> page_size:4096 prot:0800 >> [16809.973268] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16811.420048] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:6 >> page_size:4096 prot:0800 >> [16814.872686] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:5 >> page_size:4096 prot:0800 >> [16815.359099] xennet: skb rides the rocket: 21 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:20 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:5 >> page_size:4096 prot:0800 >> [16825.851906] xennet: skb rides the rocket: 20 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:19 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16828.295083] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:5 >> page_size:4096 prot:0800 >> [16837.386684] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16838.609683] xennet: skb rides the rocket: 20 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:19 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16841.783729] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:106 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:6 >> page_size:4096 prot:0800 >> [16843.841678] xennet: skb rides the rocket: 20 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:19 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> [16849.847614] xennet: skb rides the rocket: 19 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:18 offset:3690 skb_headlen:54 >> skb->len:64294, skb->data_len:64240 skb->truesize:65008 nr_frags:4 >> page_size:4096 prot:0800 >> [16853.787128] xennet: skb rides the rocket: 20 slots MAX_SKB_FRAGS: 17 >> div_roundup:1 xennet_count_skb_frag_slots:19 offset:2154 skb_headlen:1622 >> skb->len:64294, skb->data_len:62672 skb->truesize:64976 nr_frags:4 >> page_size:4096 prot:0800 >> >> # ifconfig >> eth0 Link encap:Ethernet HWaddr 00:16:3e:c4:20:46 >> inet addr:192.168.1.12 Bcast:192.168.1.255 Mask:255.255.255.0 >> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 >> RX packets:9090214 errors:0 dropped:0 overruns:0 frame:0 >> TX packets:5902090 errors:0 dropped:304 overruns:0 carrier:0 >> collisions:0 txqueuelen:1000 >> RX bytes:19757934770 (18.4 GiB) TX bytes:16855238200 (15.6 GiB) >> Interrupt:25 >> >> >> >> >> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c >> index c26e28b..50ac403 100644 >> --- a/drivers/net/xen-netfront.c >> +++ b/drivers/net/xen-netfront.c >> @@ -552,7 +552,11 @@ static int xennet_start_xmit(struct sk_buff *skb, >> struct net_device *dev) >> xennet_count_skb_frag_slots(skb); >> if (unlikely(slots > MAX_SKB_FRAGS + 1)) { >> net_alert_ratelimited( >> - "xennet: skb rides the rocket: %d slots\n", slots); >> + "xennet: skb rides the rocket: %d slots >> MAX_SKB_FRAGS: %d div_roundup:%d xennet_count_skb_frag_slots:%d offset:%d >> skb_headlen:%d skb->len:%d, skb->data_len:%d skb->truesize:%d nr_frags:%d >> page_size:%d prot:%04x \n >> + slots, MAX_SKB_FRAGS,DIV_ROUND_UP(offset + >> len, PAGE_SIZE), >> + xennet_count_skb_frag_slots(skb), offset, len, >> skb->len, >> + skb->data_len, skb->truesize, >> skb_shinfo(skb)->nr_frags, >> + PAGE_SIZE, ntohs(skb->protocol)); >> goto drop; >> } >> _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel

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