traffic bandwidth limit with dummynet
rizzo at iet.unipi.it
Fri Jun 4 12:33:17 UTC 2010
On Fri, Jun 04, 2010 at 05:25:54AM -0700, bored to death wrote:
> thank you luigi,
> your explanation really cleared everything out for me.
> i changed my pipe 1 config to:
> ipfw pipe 1 config bw 800Mbits/s queue 200K
> and set HZ to 4000
> and this solved my problem completely.
glad it helped
> i checked limitations with various values between 400Mbits/s to more than 1000Mbits/s and it works like a charm.
> (the problem was when i set queue to 80MBytes, queue value was actually set to "80 slots")
> thanks again luigi.
> From: Luigi Rizzo <rizzo at iet.unipi.it>
> To: bored to death <bored_to_death85 at yahoo.com>
> Cc: freebsd-ipfw <freebsd-ipfw at freebsd.org>
> Sent: Fri, June 4, 2010 4:27:25 PM
> Subject: Re: traffic bandwidth limit with dummynet
> On Fri, Jun 04, 2010 at 01:19:32AM -0700, bored to death wrote:
> > thank you luigi for your reply, it helped.
> > i changed the hz parameter to 1000 and then 4000 and then 8000 in my /boot/loader.conf. the result got much better.
> > i configured my system as a router and i send 1GB traffic rate passing by it and set an 800MBytes bandwidth limit on input traffic with dummynet.
> > this was the result:
> > with hz=1 (default) between 200MBytes/s and 300MBytes/s
> > with hz=1000 between 200MBytes/s and 300MBytes/s
> > with hz=4000 between 350MBytes/s and 450MBytes/s
> > with hz=8000 between 250MBytes/s and 550MBytes/s
> > the maximum traffic rate is got so much better, but 2 problems still remain:
> > 1- the maximum rate is still not high enough.
> > 2- the rate variation range is high (250-550) and it's not a steady enough.
> > i've also tried setting different "queue" and "burst" values for the pipe. the result is a little better when i set "queue" to a value between 80MBytes and 90MBytes and "burst" to a big number.
> > any other ideas?
> HZ=1000 is the default, for the records.
> Setting the burst size should have no practical effects,
> whereas setting the queue size e.g.
> ipfw pipe 10 config bw 800Mbit/s queue 200kbytes
> should help a lot, but check your configuration with 'ipfw pipe show'
> because if you supply an invalid parameter ipfw silently uses
> a default or something different.
> As an example, you said you used 80-90 Mbytes but the max queue
> size is 100 packets or 1023Kbytes and larger values do not produce
> the desired effect.
> As a rule of thumb, to make sure that drops are not caused
> by short queues, you should set the queue size to 1/HZ seconds
> worth of data -- at HZ=1000 and 1Gbit/s this means 128Kbytes.
> Note that after the dummynet queue, there might be some other
> queue that saturates. As an example, when using the box as a router,
> packets go in bursts to the output interface, and the burst can
> be as large as 1500 packets per tick on a fully saturated Gig-E
> (the interface's queue ranges normally between 128 and 1024 slots).
> The only fix for this is probably using higher values of HZ.
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