[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] xennet: skb rides the rocket: 20 slots
On 2013-1-7 18:55, Ian Campbell 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.
Today i fired up an old VM with a bittorrent client, trying to
download some torrents.
How old? Which kernel?
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.
If debug is enabled, following netback code should print out messages in
netbk_count_requests.
if (unlikely(frags >= MAX_SKB_FRAGS)) {
netdev_dbg(vif->dev, "Too many frags\n");
return -frags;
}
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.
If netback complains about "Too many frags", then it should be
MAX_SKB_FRAGS limitation in netback results in dropping packets in
netfront. It is possible that other netfronts(windows?) also hit this.
Thanks
Annie
In the meantime you could try disabling sg and/or various offloads for
that domain's vif.
[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
|
