From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Date: Mon, 09 May 2005 22:21:09 +0000 Subject: Re: [LARTC] HTB rate miscalculation Message-Id: <427FE255.9040305@dsl.pipex.com> List-Id: References: <029901c550fc$77524c30$1f00a8c0@Micro1> In-Reply-To: <029901c550fc$77524c30$1f00a8c0@Micro1> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Marcus Felipe Pereira wrote: >>> Hi, >>> I've migrated my tc configuration from CBQ to HTB. >>> >>> One problem appeared. Htb seems to miscalculate the bandwidth for >>> classes with greater rates. >>> For rates below 2Mbit there is almost no difference between the >>> configured and the measured rate. >>> >>> For large ones the problem starts. My root class has 10Mbit rate and >>> when the interface has heavy trafic the measured bandwidth coudn't >>> get more then 8.5Mbit. >>> >>> "# tc -s class show ...." shows that the root class has about the >>> 10Mbit, but the link stats shows mutch less. >>> >>> The solution was to put the htb ceil on about 12Mbit. Then I can get >>> to the 10Mbit. When using CBQ I didn't have this problem. >>> >>> Is there any parameter that I can change to correct the rate >>> calculation? >>> Any one has similar problem? >> >> >> What counters are you using to measure? >> >> Does it do the same if you test with a single tcp stream and a very >> simple setup like - >> >> tc qdisc add dev eth0 root handle 1:0 htb >> tc class add dev eth0 parent 1:0 classid 1:1 htb rate 10mbit >> tc filter add dev eth0 parent 1:0 protocol ip u32 match u32 0 0 flowid >> 1:1 >> >> Andy. > > > I've done more tests, in fact there is a difference in the measure. > > The rate measured by htb class, iptraf and iptables show very similar > numbers. > The rate measured using SNMP ifInOctets and ifOutOctets (snmpget, > ddrtool and mrtg) show rates about 20% less than htb. > > Why this difference? Not sure - I can get netperf, htb counters and polling ifconfig counters every second to agree and show correct rate with the simple case above. I don't have snmpget to test. Andy. _______________________________________________ LARTC mailing list LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc