tcpdump mailing list archives
Re: twice past the taps, thence out to net?
From: Stephen Hemminger <shemminger () vyatta com>
Date: Thu, 15 Dec 2011 10:44:40 -0800
On Thu, 15 Dec 2011 10:32:56 -0800 Rick Jones <rick.jones2 () hp com> wrote:
More exactly, we call dev_queue_xmit_nit() from dev_hard_start_xmit() _before_ giving skb to device driver. If device driver returns NETDEV_TX_BUSY, and a qdisc was setup on the device, packet is requeued. Later, when queue is allowed to send again packets, packet is retransmitted (and traced a second time in dev_queue_xmit_nit())Is this then an unintended consequence bug, or a known feature? rickYou can see the 'requeues' counter from "tc -s -d qdisc" output : qdisc mq 0: dev eth2 root Sent 29421597369 bytes 20301716 pkt (dropped 0, overlimits 0 requeues 371) backlog 0b 0p requeues 371Sure enough: $ tc -s -d qdisc qdisc mq 0: dev eth0 root Sent 2212158799862 bytes 1938268098 pkt (dropped 0, overlimits 0 requeues 4975139) backlog 0b 0p requeues 4975139 rick jones
Device's work better if the driver proactively manages stop_queue/wake_queue. Old devices used TX_BUSY, but newer devices tend to manage the queue themselves. - This is the tcpdump-workers list. Visit https://cod.sandelman.ca/ to unsubscribe.
Current thread:
- twice past the taps, thence out to net? Rick Jones (Dec 14)
- Re: twice past the taps, thence out to net? Benjamin Poirier (Dec 14)
- Re: twice past the taps, thence out to net? Vijay Subramanian (Dec 14)
- Re: twice past the taps, thence out to net? Eric Dumazet (Dec 15)
- Re: twice past the taps, thence out to net? Rick Jones (Dec 15)
- Re: twice past the taps, thence out to net? Eric Dumazet (Dec 15)
- Re: twice past the taps, thence out to net? Stephen Hemminger (Dec 15)
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- Re: twice past the taps, thence out to net? Rick Jones (Dec 15)
- Re: twice past the taps, thence out to net? Eric Dumazet (Dec 15)
- Re: twice past the taps, thence out to net? Jesse Brandeburg (Dec 16)
- Re: twice past the taps, thence out to net? Eric Dumazet (Dec 16)
- Re: twice past the taps, thence out to net? Rick Jones (Dec 16)
- Re: twice past the taps, thence out to net? Eric Dumazet (Dec 16)
- Re: twice past the taps, thence out to net? Wyborny, Carolyn (Dec 20)
- Re: twice past the taps, thence out to net? Eric Dumazet (Dec 15)
- Re: twice past the taps, thence out to net? Guy Harris (Dec 15)