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. 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 <[email protected]> To: bored to death <[email protected]> Cc: freebsd-ipfw <[email protected]> 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. o 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. chers luigi _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw To unsubscribe, send any mail to "[email protected]"
