From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f171.google.com (mail-ie0-f171.google.com [209.85.223.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id EF388200994 for ; Tue, 4 Sep 2012 08:10:37 -0700 (PDT) Received: by ieje14 with SMTP id e14so10685870iej.16 for ; Tue, 04 Sep 2012 08:10:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:x-system-of-record; bh=ijE2Tn/GOp2vfrSgCwULvczVDSnZfv6paJT4pPJNkQs=; b=FDj6OsztIb9iGiDSr3aeFGbwuYnIzhNTStqP5EgVIOc7L5HMJ6VaHdF0r2njpX9hv6 pntXGbD0Gq77dw0FIIs3+wPvXHMhNWjuTOhl4d1WtZR4P+u/ObmzvSdscBvtafwFJFb2 GUH5Ft6WrcjyolXn3FpykefL3R/s3xeSzMo2p3fy/0HGgmGUpE51wKJvyQbNuaaZ+fDd cDN5Xc1ToN0RlW5XlNMt1OcDRjh0IXR4OizmP6PvjE3ZSgv/F1vSMR/8zaQ7pWufzOZ7 RA3HDSP8cQ7sGvZqJghiQm6vkXTZzMZhSzsCJOp86FwtpKqse0lGek/g/c00c0bffH6w DI5A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:x-system-of-record:x-gm-message-state; bh=ijE2Tn/GOp2vfrSgCwULvczVDSnZfv6paJT4pPJNkQs=; b=dzgBOcEYnBtfuIuiX2/UqisS0nP+jyz9z8pHlWztUzLuqwRYOMRgVdN6vu2vPcAxnm XuODvDMQy061HYBLWNjJZp2mQfyky87zFOjjdeVKlPR1NNbBqVNKH4b/JFhaAwB2zmeE 63MxxvKk8amQNDKPin9gfgt8ceZ91kK84ia9WK1izV1U6MO+IXALnyHFjU3g/wiZvsPX 20FibYSuBd9sZceyWFdBckwNBVga7qM65CzsCRwax3ldJf13VhA9hYugntVImOisz6BO 6XyRoQmDjGlq2s4olUUbcM5/RdHNOebMGun/aM4QOU8hF6XjARwM2JjOeozMcEqNwRxC mJRA== Received: by 10.60.25.131 with SMTP id c3mr16448711oeg.50.1346771436951; Tue, 04 Sep 2012 08:10:36 -0700 (PDT) MIME-Version: 1.0 Received: by 10.60.25.131 with SMTP id c3mr16448700oeg.50.1346771436814; Tue, 04 Sep 2012 08:10:36 -0700 (PDT) Received: by 10.182.52.7 with HTTP; Tue, 4 Sep 2012 08:10:36 -0700 (PDT) In-Reply-To: <1346503884.7996.65.camel@edumazet-glaptop> References: <1346396137.2586.301.camel@edumazet-glaptop> <1346421031.2591.34.camel@edumazet-glaptop> <1346421466.2591.38.camel@edumazet-glaptop> <1346503884.7996.65.camel@edumazet-glaptop> Date: Tue, 4 Sep 2012 08:10:36 -0700 Message-ID: From: Nandita Dukkipati To: Eric Dumazet Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true X-Gm-Message-State: ALoCoQkPcA+pzCjReWJdIS2VTn7TEA4xoJ2bQPWDl/r+4uxPE/TrPwclGiG8ORXOa9U/kawX9yCC4r1mC8gyOLoI6wlIt/F9WNZHjOYIOeR+lhYdDSPLBnUV/4QBeDnXoTL0YIxuul0dCKg+lD5lgKWy4XnnHVNeE8B5tSpF0JchFpvNn7QM454wOS+75pQgjq3iNGScy76iB48gGrxZ3/1H6tp8wZm2iQ== Cc: Tomas Hruby , netdev , codel@lists.bufferbloat.net Subject: Re: [Codel] [RFC v2] fq_codel : interval servo on hosts 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: Tue, 04 Sep 2012 15:10:38 -0000 The idea of using srtt as interval makes sense to me if alongside we also hash flows with similar RTTs into same bucket. But with just the change in interval, I am not sure how codel is expected to behave. My understanding is: the interval (usually set to worst case expected RTT) is used to measure the standing queue or the "bad" queue. Suppose 1ms and 100ms RTT flows get hashed to same bucket, then the interval with this patch will flip flop between 1ms and 100ms. How is this expected to measure a standing queue? In fact I think the 1ms flow may land up measuring the burstiness or the "good" queue created by the long RTT flows, and this isn't desirable. On Sat, Sep 1, 2012 at 5:51 AM, Eric Dumazet wrote: > On Fri, 2012-08-31 at 18:37 -0700, Yuchung Cheng wrote: > >> Just curious: tp->srtt is a very rough estimator, e.g., Delayed-ACks >> can easily add 40 - 200ms fuzziness. Will this affect short flows? > > Good point > > Delayed acks shouldnt matter, because they happen when flow had been > idle for a while. > > I guess we should clamp the srtt to the default interval > > if (srtt) > q->cparams.interval = min(tcp_srtt_to_codel(srtt), > q->default_interval); > > >