61 lines
2.4 KiB
Diff
61 lines
2.4 KiB
Diff
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Subject: [Xen-devel] [PATCH] xen/netback: calculate correctly the SKB slots.
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Date: Mon, 21 May 2012 13:36:33 -0400
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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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To: xen-devel@lists.xensource.com, ian.campbell@citrix.com,
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netdev@vger.kernel.org, davem@davemloft.net, linux-kernel@vger.kernel.org
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CC: Adnan Misherfi <adnan.misherfi@oracle.com>, Konrad Rzeszutek Wilk
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<konrad.wilk@oracle.com>
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From: Adnan Misherfi <adnan.misherfi@oracle.com>
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A programming error cause the calculation of receive SKB slots to be
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wrong, which caused the RX ring to be erroneously declared full,
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and the receive queue to be stopped. The problem shows up when two
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guest running on the same server tries to communicates using large
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MTUs. Each guest is connected to a bridge with VLAN over bond
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interface, so traffic from one guest leaves the server on one bridge
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and comes back to the second guest on the second bridge. This can be
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reproduces using ping, and one guest as follow:
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- Create active-back bond (bond0)
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- Set up VLAN 5 on bond0 (bond0.5)
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- Create a bridge (br1)
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- Add bond0.5 to a bridge (br1)
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- Start a guest and connect it to br1
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- Set MTU of 9000 across the link
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Ping the guest from an external host using packet sizes of 3991, and
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4054; ping -s 3991 -c 128 "Guest-IP-Address"
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At the beginning ping works fine, but after a while ping packets do
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not reach the guest because the RX ring becomes full, and the queue
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get stopped. Once the problem accrued, the only way to get out of it
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is to reboot the guest, or use xm network-detach/network-attach.
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ping works for packets sizes 3990,3992, and many other sizes including
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4000,5000,9000, and 1500 ..etc. MTU size of 3991,4054 are the sizes
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that quickly reproduce this problem.
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Signed-off-by: Adnan Misherfi <adnan.misherfi@oracle.com>
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Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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---
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drivers/net/xen-netback/netback.c | 2 +-
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1 files changed, 1 insertions(+), 1 deletions(-)
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diff --git a/drivers/net/xen-netback/netback.c
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b/drivers/net/xen-netback/netback.c
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index 957cf9d..e382e5b 100644
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--- a/drivers/net/xen-netback/netback.c
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+++ b/drivers/net/xen-netback/netback.c
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@@ -212,7 +212,7 @@ unsigned int xenvif_count_skb_slots(struct xenvif *vif, struct sk_buff *skb)
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int i, copy_off;
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count = DIV_ROUND_UP(
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- offset_in_page(skb->data)+skb_headlen(skb), PAGE_SIZE);
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+ offset_in_page(skb->data + skb_headlen(skb)), PAGE_SIZE);
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copy_off = skb_headlen(skb) % PAGE_SIZE;
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--
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1.7.7.5
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