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Sat, 11 Jun 2016 09:11:49 +0000 To: References: <5756ADEC.9070305@darbyshire-bryant.me.uk> <8EE35B4F-5C28-41C7-8795-93A6F606B3A8@gmail.com> <5756E2CA.2020700@darbyshire-bryant.me.uk> From: Kevin Darbyshire-Bryant Message-ID: <575BD5D0.4060702@darbyshire-bryant.me.uk> Date: Sat, 11 Jun 2016 10:11:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <5756E2CA.2020700@darbyshire-bryant.me.uk> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [2001:470:183f:da2b::4007:25d] X-ClientProxiedBy: HE1PR0701CA0030.eurprd07.prod.outlook.com (10.165.214.168) To VI1PR07MB0942.eurprd07.prod.outlook.com (10.161.110.147) X-MS-Office365-Filtering-Correlation-Id: 5feab441-50d2-4c28-7494-08d391d86b8b X-Microsoft-Exchange-Diagnostics: 1; VI1PR07MB0942; 2:7qdqjsZYo4Mia+uTj4YlKpvrdtTufqZB+UxtSPORIUHPGet/SAGViodnXbykIDSjepCbiE4NcsnslceauMfnlBrhXe1K8n5uZvv5SzPB+pfcfOpoJ0yotPSVmBVMbSar1JMNZBH8C55uDeH4MYe/w2BnZEbEtFRuOQlD5ZlPbs+Dj6s0qomlqkuDPtqonGJ7; 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VI1PR07MB0942; 6:LHGiWuH3ecMVySUo4mvCiIr2YcNrwkP+uFt8vO1uEOamX829OTdNsupNI3j9tz5r6xdl0AG1rbwTxBw7VcXksbbak5/cXL+Bg4/80E7uW8NHQ18/mMVqfDsOjmcwp8A7y0H1R5ALxwTRvdkHh1sWnEwn9gzadLdzNQBmquVUNjSQ2D6ForITRTOxxQTcUWH934PLUi1g4EzVoiYAb4urignCtuneeOR/B5RX/FSPbCVR/MWusdxQTL7fHT/lHUCik1vS1+aW6ZsX0/PuSnsnyGRf/OIsKxAL5+9fLeBNW8Yb93Db+pQEX5YQcGLaDm2e; 5:ISk4m81/WGNAjbngDi8SbGv0Kd7XmhVDok46c1cYrLa+p+7YR3sYw63IIcFGyaTFLWKgWDnGv2K27N5zTZ3Q/sNibYLMqbJothxikqPMfZcAN3u4eq9YXOxUn9s3GSIt4+jhF6VTWns6HNnLW+eb9g==; 24:vYukLkn0t/mFKdhyjgaP2E5fj+f3JaztX/5x6hDdZdPewd0SAE+dZjVkOtn1yAM9B/G0k4bTRignTX/eoqYtCD+ASz6CNIwxdTO3+yJqM1k=; 7:4ssE1xC6xHfTjTY4fbIhI7whDlnDjw5vvBwChgHwu52wmBfFGfLfuCLumFIaVi5o13dCPYiPcNTNUSZ1CN+ignwJdt+7VXIdkzlxoj+a0nzzYbDi7ckELzz+qWwl/ebgnfR1QLoV5l9iyQnn8NBeyQXKh0WG9K9qEdKQKXnxWh+HJxMCS8znKDAmPOAfqeEcm00yXnfAj7Dc7vOpa1R1cRIewNLVVP/H409s8T/T14I= SpamDiagnosticOutput: 1:99 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: darbyshire-bryant.me.uk X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Jun 2016 09:11:49.0024 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR07MB0942 Subject: Re: [Cake] Possible BUG - parent backlog incorrectly updated in case of NET_XMIT_CN 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: Sat, 11 Jun 2016 09:11:52 -0000 On 07/06/16 16:05, Kevin Darbyshire-Bryant wrote: > > > On 07/06/16 15:50, Jonathan Morton wrote: >>> On 7 Jun, 2016, at 14:20, Kevin Darbyshire-Bryant >>> wrote: >>> >>> I had a nose at CAKE but couldn't quit work out if a similar issue >>> is present but I suspect it is. Certainly if Eric can't get it right >>> "My prior attempt to fix the backlogs of parents failed." then it's >>> not an 'obvious to solve' problem :-) >> It appears my code already handles it correctly. This is most likely >> because it inherited the analogous handling from the old function >> called here. > > I was intrigued by how in the case of XMIT_CN he reports the backlog > without the packet just dropped 'cos the parent qdisc won't include > that length in its calculations because we reported we dropped the > packet. Preventing double accounting. > > + /* As we dropped packet(s), better let upper stack know this. > + * If we dropped a packet for this flow, return NET_XMIT_CN, > + * but in this case, our parents wont increase their backlogs. > + */ > + prev_qlen -= sch->q.qlen; > + prev_backlog -= sch->qstats.backlog; > + if (ret == idx) { > + qdisc_tree_reduce_backlog(sch, prev_qlen - 1, > + prev_backlog - qdisc_pkt_len(skb)); <<< + return NET_XMIT_CN; > + } > + qdisc_tree_reduce_backlog(sch, prev_qlen, prev_backlog); > + return NET_XMIT_SUCCESS; And now there's a version 2 of Eric's fix: http://marc.info/?l=linux-netdev&m=146507012302643&w=2 Does this change apply to cake? Cheers, Kevin