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From: Yang Yingliang <yangyingliang@huawei.com>
To: Eric Dumazet <edumazet@google.com>
Cc: <netdev@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>
Subject: net_sched: precision problem of TBF/HTB
Date: Tue, 16 Jul 2013 12:12:05 +0800	[thread overview]
Message-ID: <51E4C815.9000408@huawei.com> (raw)

Hi, Eric
Commit 1def9238d4aa2 (net_sched: more precise pkt_len computation) makes more precise transfer bytes by taking account of headers in qdisc_skb_cb(skb)->pkt_len, but this introduces a problem with calculating bandwidth in userland.

When calculating bandwidth in userland, it's not include headers' bytes. From the user's perspective, it's not a correct bandwidth.

Shall we need take account of headers in qdisc_skb_cb(skb)->pkt_len or just skb->len?

Example:
tc qdisc add dev $DEV root handle 1: tbf latency 50ms burst 500kB rate 500mbit mtu 64k

iperf -c host -t 30 -i 10
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec   571 MBytes   479 Mbits/sec
[  3] 10.0-20.0 sec   570 MBytes   478 Mbits/sec
[  3] 20.0-30.0 sec   570 MBytes   478 Mbits/sec
[  3]  0.0-30.0 sec  1.67 GBytes   478 Mbits/sec

             reply	other threads:[~2013-07-16  4:12 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-16  4:12 Yang Yingliang [this message]
2013-07-16  4:50 ` net_sched: precision problem of TBF/HTB Eric Dumazet
2013-07-17  1:41   ` Ding Tianhong
2013-07-17  3:18     ` John Fastabend

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