From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ding Tianhong Subject: Re: net_sched: precision problem of TBF/HTB Date: Wed, 17 Jul 2013 09:41:03 +0800 Message-ID: <51E5F62F.8080906@huawei.com> References: <51E4C815.9000408@huawei.com> <1373950201.10804.103.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Yang Yingliang , Eric Dumazet , , "David S. Miller" To: Eric Dumazet Return-path: Received: from szxga02-in.huawei.com ([119.145.14.65]:29170 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971Ab3GQBlg (ORCPT ); Tue, 16 Jul 2013 21:41:36 -0400 In-Reply-To: <1373950201.10804.103.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On 2013/7/16 12:50, Eric Dumazet wrote: > On Tue, 2013-07-16 at 12:12 +0800, Yang Yingliang wrote: >> 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. >> > This changed nothing to 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? >> > These values are not accessible from userland, unless you capture > packets with a sniffer (tcpdump or something like that) > >> 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 > > > iperf only measures the amount of payload, and probably do not care of > headers. > > You cannot accurately measure bandwidth from userland, unless making > assumptions (or getting them from the stack) on header sizes (IP + TCP), > MSS value, and retransmits. > > ok, for the further, can you give me some advise for how calculate the bandwidth for net link. for example,what kind of tools is better. > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > >