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[156.34.55.100]) by smtp.gmail.com with ESMTPSA id c4sm98515qkd.24.2019.06.13.10.23.55 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 13 Jun 2019 10:23:55 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hbTS7-00034X-97; Thu, 13 Jun 2019 14:23:55 -0300 Date: Thu, 13 Jun 2019 14:23:55 -0300 From: Jason Gunthorpe To: =?utf-8?B?SMOla29u?= Bugge Cc: Doug Ledford , Leon Romanovsky , Parav Pandit , Steve Wise , OFED mailing list , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] RDMA/cma: Make CM response timeout and # CM retries configurable Message-ID: <20190613172355.GF22901@ziepe.ca> References: <20190226075722.1692315-1-haakon.bugge@oracle.com> <174ccd37a9ffa05d0c7c03fe80ff7170a9270824.camel@redhat.com> <67B4F337-4C3A-4193-B1EF-42FD4765CBB7@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <67B4F337-4C3A-4193-B1EF-42FD4765CBB7@oracle.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 13, 2019 at 06:58:30PM +0200, Håkon Bugge wrote: > If you refer to the backlog parameter in rdma_listen(), I cannot see > it being used at all for IB. > > For CX-3, which is paravirtualized wrt. MAD packets, it is the proxy > UD receive queue length for the PF driver that can be construed as a > backlog. No, in IB you can drop UD packets if your RQ is full - so the proxy RQ is really part of the overall RQ on QP1. The backlog starts once packets are taken off the RQ and begin the connection accept processing. > Customer configures #VMs and different workload may lead to way > different number of CM connections. The proxying of MAD packet > through the PF driver has a finite packet rate. With 64 VMs, 10.000 > QPs on each, all going down due to a switch failing or similar, you > have 640.000 DREQs to be sent, and with the finite packet rate of MA > packets through the PF, this takes more than the current CM > timeout. And then you re-transmit and increase the burden of the PF > proxying. I feel like the performance of all this proxying is too low to support such a large work load :( Can it be improved? Jason