From owner-freebsd-ipfw@FreeBSD.ORG Fri Jun 4 11:46:56 2010 Return-Path: Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B3CC21065674 for ; Fri, 4 Jun 2010 11:46:56 +0000 (UTC) (envelope-from luigi@onelab2.iet.unipi.it) Received: from onelab2.iet.unipi.it (onelab2.iet.unipi.it [131.114.59.238]) by mx1.freebsd.org (Postfix) with ESMTP id 7987E8FC26 for ; Fri, 4 Jun 2010 11:46:56 +0000 (UTC) Received: by onelab2.iet.unipi.it (Postfix, from userid 275) id CFE0F73098; Fri, 4 Jun 2010 13:57:25 +0200 (CEST) Date: Fri, 4 Jun 2010 13:57:25 +0200 From: Luigi Rizzo To: bored to death Message-ID: <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <360703.24596.qm@web59711.mail.ac4.yahoo.com> User-Agent: Mutt/1.4.2.3i Cc: freebsd-ipfw Subject: Re: traffic bandwidth limit with dummynet X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Jun 2010 11:46:56 -0000 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