From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f171.google.com (mail-we0-f171.google.com [74.125.82.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 8C48D2012AC for ; Sat, 5 May 2012 16:07:24 -0700 (PDT) Received: by wejx9 with SMTP id x9so4609337wej.16 for ; Sat, 05 May 2012 16:07:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; bh=1KCs5H4VvbACn7P4vGdF57MgqTVFUFQ8ruMuJPgFsyo=; b=etA8VZRqCfOMHV7SphwwZSltk3rcQ9NJxlFku4EQWQ7KB0sXOWqm4hHHV5Q2jadkAu 6f8SzRyKpAvkzjntkt2wYYT7SNWP/MwyJR4N3gJhN55kgQC6kX6Dy7xXjO5LiraUiyNT GhuEp2VVVewPRQnZYRPD4pGNpv0r4nS0ePEd+TVrvqGb7iRuhp5mIzEv1ZlDcPFaoiMW 2yTkrX/lCTy7iFD8QlX4Q2ICLEpE0MmCNustR+f9JIczTqgutzQcZrzqQCoYp8HglgdK VVsAIrzD9JLqyd9OeqqxUbnqHpguFCFs0hVvsjBdMZqGWgrBkQztU7KtE3JslNlX7rdV Yxdg== Received: by 10.216.143.200 with SMTP id l50mr4656547wej.58.1336259241496; Sat, 05 May 2012 16:07:21 -0700 (PDT) Received: from [172.28.130.107] ([74.125.122.49]) by mx.google.com with ESMTPS id gd4sm14450591wib.6.2012.05.05.16.07.19 (version=SSLv3 cipher=OTHER); Sat, 05 May 2012 16:07:20 -0700 (PDT) From: Eric Dumazet To: dave taht In-Reply-To: <4FA5AE25.1080506@gmail.com> References: <1336217671-20384-1-git-send-email-dave.taht@bufferbloat.net> <1336218794.3752.508.camel@edumazet-glaptop> <1336229343.3752.516.camel@edumazet-glaptop> <1336249251.3752.558.camel@edumazet-glaptop> <1336250168.3752.560.camel@edumazet-glaptop> <1336252281.3752.561.camel@edumazet-glaptop> <4FA597C0.7090206@gmail.com> <1336252832.3752.563.camel@edumazet-glaptop> <4FA5A3B8.7020808@gmail.com> <1336255783.3752.573.camel@edumazet-glaptop> <4FA5AB05.9030305@gmail.com> <1336257554.3752.578.camel@edumazet-glaptop> <4FA5AE25.1080506@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Sun, 06 May 2012 01:07:18 +0200 Message-ID: <1336259238.3752.611.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Cc: codel@lists.bufferbloat.net, Dave =?ISO-8859-1?Q?T=E4ht?= Subject: Re: [Codel] [PATCH v5] pkt_sched: codel: Controlled Delay AQM X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 05 May 2012 23:07:25 -0000 On Sat, 2012-05-05 at 15:48 -0700, dave taht wrote: > Stalking butterflies. ( > http://en.wikipedia.org/wiki/File:Lorenz_attractor_yb.svg ) > > I suspected also we would have issues as we hit some natural quantums > (clock rate/interrupt rate/bql estimator etc) but for all I know it's > just a plain bug. I need a reboot. Goin to dinner. > This part of Codel seems suspicious (last page ) // If min went above target close to when we last went below it // assume that the drop rate that controlled the queue on the // last cycle is a good starting point to control it now. if (now - drop_next < 16.*interval) { int c = count - 1; count = c<1? 1 : c; else { count = 1; } I suggest to replace it by a more conservative algo : // If min went above target close to when we last went below it // assume that sqrt(half) the drop rate that controlled the queue on the // last cycle is a good starting point to control it now. if (now - drop_next < 16.*interval) { int c = count >> 1; count = c<1? 1 : c; else { count = 1; } With this change, my q->count max value is 12000