Date: Fri, 4 Jun 2010 11:30:46 -0500 From: Brandon Gooch <jamesbrandongooch@gmail.com> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: freebsd-ipfw <freebsd-ipfw@freebsd.org>, bored to death <bored_to_death85@yahoo.com> Subject: Re: traffic bandwidth limit with dummynet Message-ID: <AANLkTinYPfJUrX8OHx5oc1xSySVIJqmaPdztoOMkqcFw@mail.gmail.com> In-Reply-To: <20100604115725.GA37274@onelab2.iet.unipi.it> References: <247123.29322.qm@web59713.mail.ac4.yahoo.com> <20100603172733.GA16454@onelab2.iet.unipi.it> <360703.24596.qm@web59711.mail.ac4.yahoo.com> <20100604115725.GA37274@onelab2.iet.unipi.it>
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On Fri, Jun 4, 2010 at 6:57 AM, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > 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 /bo= ot/loader.conf. the result got much better. >> i configured my system as a router and i send 1GB traffic rate passing b= y it and set an 800MBytes bandwidth limit on input traffic with dummynet. >> this was the result: >> with hz=3D1 (default) between 200MBytes/s and 300MBytes/s >> with hz=3D1000 between 200MBytes/s and 300MBytes/s >> with hz=3D4000 between 350MBytes/s and 450MBytes/s >> with hz=3D8000 between 250MBytes/s and 550MBytes/s >> >> the maximum traffic rate is got so much better, but 2 problems still rem= ain: >> 1- the maximum rate is still not high enough. >> 2- the rate variation range is high (250-550) and it's not a steady enou= gh. >> >> i've also tried setting different "queue" and "burst" values for the pip= e. the result is a little better when i set "queue" to a value between 80MB= ytes and 90MBytes and "burst" to a big number. >> >> any other ideas? >> > > HZ=3D1000 is the default, for the records. > Setting the burst size should have no practical effects, > whereas setting the queue size e.g. > o > =A0 =A0 =A0 =A0ipfw 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=3D1000 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. > > chers > luigi Thanks for the explanation Luigi, this is bound to help others in regard to queue configuration. -Brandon
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