From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.toke.dk (mail.toke.dk [52.28.52.200]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id F2A9F3CB43 for ; Thu, 22 Nov 2018 16:05:32 -0500 (EST) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=toke.dk; s=20161023; t=1542920731; bh=ibi7Yy0nuisTLkE2A7LfibfmCklgz3J0SZZeeXceGT4=; h=From:To:Subject:In-Reply-To:References:Date:From; b=EN28/SI8sjg9/wY9OGA4xpA2QIBnJ9Mb+q5aLOeOA6VJtYeL0lYf4nON9YE7Mh9Oh OhemYTCzd7QwFQmtWwxF47DvvPZEqmObFBiTInljJUKEIijN+qPgkB17rufDujaqOl GOgTARpxd/5riyowawfKZdyY9wLVZj+AKW3M9XLYSNwbmFeMk9zbKyl+ONwqNs9NmT DX02v1vqLnJ9iP/FpBAmSF3OjVoNQiFL+d3Q1Xq6Pg5txtlb46UMi+J21W+HCHznEP TyiFxEP+UVlDleq/upB64BWe4UJRtqeQDNmaaH+IAeEdL+9V2aQonqtUwfFdOeK1RH apAwX+YQMVDwg== To: Fabian Ruffy , cake@lists.bufferbloat.net In-Reply-To: <477d23a4-724c-2601-2cb2-ce1f0c0910f2@cs.ubc.ca> References: <477d23a4-724c-2601-2cb2-ce1f0c0910f2@cs.ubc.ca> Date: Thu, 22 Nov 2018 22:05:29 +0100 X-Clacks-Overhead: GNU Terry Pratchett Message-ID: <87r2fczuue.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Cake] Emulating Bufferbloat X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 22 Nov 2018 21:05:33 -0000 Fabian Ruffy writes: > Hello, > > this is a somewhat esoteric question. I am trying to actually force buffe= rbloat > in an emulation setup I am using. I set up a dumbbell topology and push t= raffic > through it, causing congestion at the central link. I use this setup to c= ompare > congestion avoidance algorithms such as DCTCP to other solutions. > This has worked nicely with the 4.18 kernel. However, after upgrading to = 4.19 I > cannot reproduce bufferbloat anymore. The traffic (even UDP packets) is > perfectly rate limited and I never see any congestion happening. This is = great, > but in practice it prevents me from prototyping algorithms. Ha, that's awesome! :D > My interface configuration for bottlenecked links is: > > qdisc tbf 5: dev OBcbnsw1-eth2 root refcnt 2 rate 10Mbit burst 15000b= lat > 12.0ms > =C2=A0Sent 6042 bytes 51 pkt (dropped 0, overlimits 0 requeues 0) > =C2=A0backlog 0b 0p requeues 0 > qdisc netem 10: dev OBcbnsw1-eth2 parent 5:1 limit 500 > =C2=A0Sent 6042 bytes 51 pkt (dropped 0, overlimits 0 requeues 0) > =C2=A0backlog 0b 0p requeues 0 > > > I have the suspicion that it is related to the CAKE changes in the 4.19 k= ernel, > but I am not exactly sure. I am not using tc cake at all. Do you maybe kn= ow > what could cause this behavior? Apologies if this is the wrong mailing > list. My guess would be changes in the TCP stack; can't point you to anything specific off the top of my head, though... -Toke