From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f49.google.com (mail-wm0-f49.google.com [74.125.82.49]) by dpdk.org (Postfix) with ESMTP id 974942BDC for ; Wed, 14 Sep 2016 16:30:48 +0200 (CEST) Received: by mail-wm0-f49.google.com with SMTP id 1so34869757wmz.1 for ; Wed, 14 Sep 2016 07:30:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=6wind-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=CBnNc3rdKNF0AdG1ipg0P9tV4AW5q9Bi8Ud6Jp75kM8=; b=hp4BjY5+z/BqDpwc5zhORh2gfqATTDA71SHQ9DfjkAYWBe6AH69HsEDtsdT9Tpe+/5 i6evCLwe9y5UTB4rmwPyEzg5jtjFjizpTQ3svUInL5gQXIP/oN8E8xCARKfbP6Z9GOGE 9gdUrFqtfAMSMjitOf2zOHf2jxHXwyliE3YKnwwpKNIrshYgIswGLLt44+PJ0z4cD/3Y oXYnGK+2bQdQRTxiliYMGg+MTSY+ytO2Tm3ZX13eM8X3dWVGIUK8Lfq8Ajx78hNB87wM hHK7APvq8V3oLyDTdU9cGaJ8KmJCrMgdMuWzNm5v0gbNq4oPbYESncPdEP9NrdbUwDsy yFog== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=CBnNc3rdKNF0AdG1ipg0P9tV4AW5q9Bi8Ud6Jp75kM8=; b=EoqdTZBHsChY1EoWRnqCRdfD7Lj0Wd7KrkrqUm38neRfT8xBUR6TZad5TSQgyiEyS4 V/L6aujUCEUyQ3Cv204R2JpVLINtAXL4wWJtPR3Nyqmn/OsfHQQmsqJPj8HXR3WbXA8V Ff4VSFpegr941iHtmEPOy5gMx+NA3Hc2YnFkkvvVyG04IEgS7zuvwoljKkSVQNVkwnEe /HXNkQaRdib77sJH82tL37IRcZNf0yuooyzt013Vbb03QX4PWvuDAEP4BLqa/YZv4cro Dz/IYJAR/KX3Rk/WOlBchRaWWR3+IFVUmY2bxdpCr42DF6t/TN5C2mNYFc0pgqeU2Uqi 6Onw== X-Gm-Message-State: AE9vXwMHhVel3LeNynGTEsd6IUFIYgl2cnp139X9t/PNvZf7rnbcImNoP9ovsAGMbQLMF7iw X-Received: by 10.194.192.195 with SMTP id hi3mr2929124wjc.108.1473863448359; Wed, 14 Sep 2016 07:30:48 -0700 (PDT) Received: from 6wind.com (guy78-3-82-239-227-177.fbx.proxad.net. [82.239.227.177]) by smtp.gmail.com with ESMTPSA id r8sm4490547wjs.22.2016.09.14.07.30.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 14 Sep 2016 07:30:47 -0700 (PDT) Date: Wed, 14 Sep 2016 16:30:34 +0200 From: Adrien Mazarguil To: Luke Gorrie Cc: "dev@dpdk.org" Message-ID: <20160914143016.GT17252@6wind.com> Mail-Followup-To: Luke Gorrie , "dev@dpdk.org" References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [dpdk-dev] Possible bug in mlx5_tx_burst_mpw? X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 Sep 2016 14:30:48 -0000 Hi Luke, On Wed, Sep 14, 2016 at 03:24:07PM +0200, Luke Gorrie wrote: > Howdy, > > Just noticed a line of code that struck me as odd and so I am writing just > in case it is a bug: > > http://dpdk.org/browse/dpdk/tree/drivers/net/mlx5/mlx5_rxtx.c#n1014 > > Specifically the check "(mpw.length != length)" in mlx_tx_burst_mpw() looks > like a descriptor-format optimization for the special case where > consecutive packets on the wire are exactly the same size. This would > strike me as peculiar. > > Just wanted to check, is that interpretation correct and if so then is this > intentional? Your interpretation is correct (this is intentional and not a bug). In the event successive packets share a few properties (length, number of segments, offload flags), these can be factored out as an optimization to lower the amount of traffic on the PCI bus. This feature is currently supported by the ConnectX-4 Lx family of adapters. -- Adrien Mazarguil 6WIND