From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antonio Almeida Subject: HTB accuracy for high speed Date: Fri, 15 May 2009 15:49:31 +0100 Message-ID: <298f5c050905150749s3597328dr8dd15adbd7a37532@mail.gmail.com> References: <298f5c050905150745p13dc226eia1ff50ffa8c4b300@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE To: netdev@vger.kernel.org, jarkao2@gmail.com, kaber@trash.net, davem@davemloft.net, devik@cdi.cz Return-path: Received: from fg-out-1718.google.com ([72.14.220.158]:56318 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752461AbZEOOtd convert rfc822-to-8bit (ORCPT ); Fri, 15 May 2009 10:49:33 -0400 Received: by fg-out-1718.google.com with SMTP id d23so140361fga.17 for ; Fri, 15 May 2009 07:49:32 -0700 (PDT) In-Reply-To: <298f5c050905150745p13dc226eia1ff50ffa8c4b300@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Hi! I've been using HTB in a Linux bridge and recently I noticed that, for high speed, the configured rate/ceil is not respected as for lower speeds. I'm using a packet generator/analyser to inject over 950Mpbs, and see what returns back to it, in the other side of my bridge. Generated packets have 800bytes. I noticed that, for several tc HTB rate/ceil configurations the amount of traffic received by the analyser stays the same. See this values: HTB conf=A0=A0=A0=A0=A0 Analyser reception 476000Kbit=A0=A0=A0 544.260.329 500000Kbit=A0=A0=A0 545.880.017 510000Kbit=A0=A0=A0 544.489.469 512000Kbit=A0=A0=A0 546.890.972 ------------------------- 513000Kbit=A0=A0=A0 596.061.383 520000Kbit=A0=A0=A0 596.791.866 550000Kbit=A0=A0=A0 596.543.271 554000Kbit=A0=A0=A0 596.193.545 ------------------------- 555000Kbit=A0=A0=A0 654.773.221 570000Kbit=A0=A0=A0 654.996.381 590000Kbit=A0=A0=A0 655.363.253 605000Kbit=A0=A0=A0 654.112.017 ------------------------- 606000Kbit=A0=A0=A0 728.262.237 665000Kbit=A0=A0=A0 727.014.365 ------------------------- There are these steps and it looks like doesn't matter if I configure HTB to 555Mbit or to 605Mbit - the result is the same: 654Mbit. This is 18% more traffic than the configured value. I also realise that for smaller packets it gets worse, reaching 30% more traffic than what I configured. For packets of 1514bytes the accuracy is quiet good. I'm using kernel 2.6.25 My 'tc -s -d class ls dev eth1' output: class htb 1:10 parent 1:2 rate 1000Mbit ceil 1000Mbit burst 126375b/8 mpu 0b overhead 0b cburst 126375b/8 mpu 0b overhead 0b level 5 =A0Sent 51888579644 bytes 62067679 pkt (dropped 0, overlimits 0 requeue= s 0) =A0rate 653124Kbit 97656pps backlog 0b 0p requeues 0 =A0lended: 0 borrowed: 0 giants: 0 =A0tokens: 113 ctokens: 113 class htb 1:1 root rate 1000Mbit ceil 1000Mbit burst 126375b/8 mpu 0b overhead 0b cburst 126375b/8 mpu 0b overhead 0b level 7 =A0Sent 51888579644 bytes 62067679 pkt (dropped 0, overlimits 0 requeue= s 0) =A0rate 653123Kbit 97656pps backlog 0b 0p requeues 0 =A0lended: 0 borrowed: 0 giants: 0 =A0tokens: 113 ctokens: 113 class htb 1:2 parent 1:1 rate 1000Mbit ceil 1000Mbit burst 126375b/8 mpu 0b overhead 0b cburst 126375b/8 mpu 0b overhead 0b level 6 =A0Sent 51888579644 bytes 62067679 pkt (dropped 0, overlimits 0 requeue= s 0) =A0rate 653124Kbit 97656pps backlog 0b 0p requeues 0 =A0lended: 0 borrowed: 0 giants: 0 =A0tokens: 113 ctokens: 113 class htb 1:108 parent 1:10 leaf 108: prio 7 quantum 1514 rate 555000Kbit ceil 555000Kbit burst 70901b/8 mpu 0b overhead 0b cburst 70901b/8 mpu 0b overhead 0b level 0 =A0Sent 51888579644 bytes 62067679 pkt (dropped 27801917, overlimits 0 = requeues 0) =A0rate 653124Kbit 97656pps backlog 0b 0p requeues 0 =A0lended: 62067679 borrowed: 0 giants: 0 =A0tokens: -798 ctokens: -798 As you can see, class htb 1:108 rate's is 653124Kbit! Much bigger that it's ceil. I also note that, for HTB rate configurations over 500Mbit/s on leaf class, when I stop the traffic, in the output of "tc -s -d class ls dev eth1" command, I see that leaf's rate (in bits/s) is growing instead of decreasing (as expected since I've stopped the traffic). Rate in pps is ok and decreases until 0pps. Rate in bits/s increases above 1000Mbit and stays there for a few minutes. After two or three minutes it becomes 0bit. The same happens for it's ancestors (also for root class).Here's tc output of my leaf class for this situation: class htb 1:108 parent 1:10 leaf 108: prio 7 quantum 1514 rate 555000Kbit ceil 555000Kbit burst 70901b/8 mpu 0b overhead 0b cburst 70901b/8 mpu 0b overhead 0b level 0 =A0Sent 120267768144 bytes 242475339 pkt (dropped 62272599, overlimits = 0 requeues 0) =A0rate 1074Mbit 0pps backlog 0b 0p requeues 0 =A0lended: 242475339 borrowed: 0 giants: 0 =A0tokens: 8 ctokens: 8 =A0 Antonio Almeida