From: Bruce Richardson <bruce.richardson@intel.com>
To: Tom Kiely <tkiely@brocade.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] Question about zero length segments in received mbuf
Date: Fri, 16 Oct 2015 15:00:02 +0100 [thread overview]
Message-ID: <20151016140002.GH9980@bricha3-MOBL3> (raw)
In-Reply-To: <5620FC5F.30307@brocade.com>
On Fri, Oct 16, 2015 at 02:32:15PM +0100, Tom Kiely wrote:
> Hi,
> I am currently experiencing a serious issue and was hoping someone else
> might have encountered it.
>
> I have a KVM VM using two ixgbe interfaces A and B (configured to use PCI
> passthrough) and forwarding traffic from interface A via B.
> At about 4 million pps of 64 byte frames, the rx driver
> ixgbe_recv_scattered_pkts_vec() appears to be generating mbufs with 2
> segments, the first of which has data_len ==0 and the second data_len==64.
> The real problem is that when ixgbe_xmit_pkts() on the tx side gets about 18
> of these packets, it seems to mess up the transmit descriptor handling.
> ixgbe_xmit_cleanup() never sees the STAT_DD bit set and no descriptor get
> freed leading to total traffic loss.
>
> I'm still debugging the xmit side to find out what's causing the descriptor
> ring problem.
>
> Has anyone encountered the rx side zero-length-segment issue ? I found a
> reference to such an issue on the web but it was years old.
>
> I'm using DPDK 1.8.0.
>
> Any information gratefully received,
> Tom
Hi Tom,
on the TX side, if these two-segment packets are getting sent to the NIC, you
probably want to make sure that the TX code is set up to handle multi-segment
packets. By default in most drivers, the NO_MULTISEG flag is set on queue
initialization.
/Bruce
prev parent reply other threads:[~2015-10-16 14:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-16 13:32 Tom Kiely
2015-10-16 14:00 ` Bruce Richardson [this message]
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