Date: Mon, 2 Aug 2010 11:22:07 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Patrick Mahan <mahan@mahan.org> Cc: freebsd-net@freebsd.org Subject: Re: AltQ throughput issues (long message) Message-ID: <20100802092207.GC2054@onelab2.iet.unipi.it> In-Reply-To: <4C544ADC.2050109@mahan.org> References: <4C535B18.8020205@mahan.org> <20100730233053.GA12554@onelab2.iet.unipi.it> <4C544ADC.2050109@mahan.org>
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On Sat, Jul 31, 2010 at 09:10:04AM -0700, Patrick Mahan wrote:
...
> >part of it can be explained because AltQ counts the whole packet
> >(eg. 1514 bytes for a full frame) whereas iperf only considers the
> >UDP payload (e.g. 1470 bytes in your case).
> >
>
> Okay, but that only accounts for 3% and I am seeing around 11%, any
> idea what might be accounting for the remaining 8%?
no, sometimes the extra icmp traffic plays a role, sometimes
it is just the shaper that is not precise and has systematic
errors (due to rounding in computing intervals and delays).
I cannot comment precisely on AltQ because i don't know
enough about its internals.
> >The other thing you should check is whether there is any extra
> >traffic going through the interface that competes for the bottleneck
> >bandwidth. You have such huge drop rates in your tests that i
> >would not be surprised if you had ICMP packets going around
> >trying to slow down the sender.
...
> Where do you see the drop? If you are looking at the end of the pfctl
iperf reports show that it is dropping tons of packets (see below, Lost/Total)
> >>npx8# iperf -c 172.16.13.10 -p 7788 -u -b 25M -u -i 30 -t 200
> >>------------------------------------------------------------
> >>Client connecting to 172.16.13.60, UDP port 7788
> >>Sending 1470 byte datagrams
> >>UDP buffer size: 9.00 KByte (default)
> >>------------------------------------------------------------
> >>[ 3] local 172.16.13.60 port 7788 connected with 172.16.38.80 port 41064
> >>[ ID] Interval Transfer Bandwidth Jitter Lost/Total
> >>Datagrams
> >>[ 3] 0.0-30.0 sec 5.96 MBytes 1.67 Mbits/sec 0.710 ms 59453/63706
> >>(93%)
> >>[ ID] Interval Transfer Bandwidth Jitter Lost/Total
> >>Datagrams
> >>[ 3] 30.0-60.0 sec 5.95 MBytes 1.66 Mbits/sec 0.736 ms 59616/63859
> >>(93%)
> >
> >BTW have you tried dummynet in your config?
> >
>
> How would you suggest using dummynet? Is it workable for a QoS solution?
Very workable. see http://info.iet.unipi.it/~luigi/dummynet/
especially the video/slides at the top of the page.
cheers
luigi
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