From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f46.google.com (mail-qg0-f46.google.com [209.85.192.46]) by dpdk.org (Postfix) with ESMTP id 002A67E6A for ; Fri, 11 Sep 2015 17:12:39 +0200 (CEST) Received: by qgx61 with SMTP id 61so64879785qgx.3 for ; Fri, 11 Sep 2015 08:12:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=yI3FZNNCA9U6TrGxXUA/8iJ76MGo3+5MmIvd7wOav3A=; b=UVq8pqaZNOAOE0HzRrM2yMSx6W2byhAjd4Jgc67gG6/UCwxZdxS1fw1fllLQABmjy0 q4EUjrbXXec1YeeCNja33yzeXayj3Nx4bId8OOq9I92BiE14Kd3DB/bhjpJMFjQSqbEj i4Puc+xje91VsBmM/7F0010b8DX4KyeqmAFSDny8zHAortP8rl4U51VAT/P9+X4J46gu KV9a2ZvE4BX3RXfkVDbygjjOg38JCiiXzBH2wUjpIjEA3zp1z92IVnsOEJi1rBMfs1BG BT9boxEgVUdM7NVPWiu6JbTLuvuYimjP4PJl6heCbtSDI9bsXJz5rMQDyczPDFZ3sHz2 /Opw== X-Gm-Message-State: ALoCoQmdvncgIenH8D+9yIL9IIVkK8d17NqR5pxTEBgbAxnF30TzhuYfu1cWc07YfUc09QCayxFg MIME-Version: 1.0 X-Received: by 10.140.152.203 with SMTP id 194mr66360958qhy.47.1441984359281; Fri, 11 Sep 2015 08:12:39 -0700 (PDT) Received: by 10.55.123.131 with HTTP; Fri, 11 Sep 2015 08:12:39 -0700 (PDT) Received: by 10.55.123.131 with HTTP; Fri, 11 Sep 2015 08:12:39 -0700 (PDT) In-Reply-To: <1762144.1LKiyImgC1@xps13> References: <1439489195-31553-1-git-send-email-vladz@cloudius-systems.com> <55F2E448.1070602@6wind.com> <55F2E997.5050009@cloudius-systems.com> <1762144.1LKiyImgC1@xps13> Date: Fri, 11 Sep 2015 18:12:39 +0300 Message-ID: From: Vladislav Zolotarov To: Thomas Monjalon Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1 for all NICs but 82598 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: Fri, 11 Sep 2015 15:12:40 -0000 On Sep 11, 2015 5:55 PM, "Thomas Monjalon" wrote: > > 2015-09-11 17:47, Avi Kivity: > > On 09/11/2015 05:25 PM, didier.pallard wrote: > > > On 08/25/2015 08:52 PM, Vlad Zolotarov wrote: > > >> > > >> Helin, the issue has been seen on x540 devices. Pls., see a chapter > > >> 7.2.1.1 of x540 devices spec: > > >> > > >> A packet (or multiple packets in transmit segmentation) can span any > > >> number of > > >> buffers (and their descriptors) up to a limit of 40 minus WTHRESH > > >> minus 2 (see > > >> Section 7.2.3.3 for Tx Ring details and section Section 7.2.3.5.1 for > > >> WTHRESH > > >> details). For best performance it is recommended to minimize the > > >> number of buffers > > >> as possible. > > >> > > >> Could u, pls., clarify why do u think that the maximum number of data > > >> buffers is limited by 8? > > >> > > >> thanks, > > >> vlad > > > > > > Hi vlad, > > > > > > Documentation states that a packet (or multiple packets in transmit > > > segmentation) can span any number of > > > buffers (and their descriptors) up to a limit of 40 minus WTHRESH > > > minus 2. > > > > > > Shouldn't there be a test in transmit function that drops properly the > > > mbufs with a too large number of > > > segments, while incrementing a statistic; otherwise transmit function > > > may be locked by the faulty packet without > > > notification. > > > > > > > What we proposed is that the pmd expose to dpdk, and dpdk expose to the > > application, an mbuf check function. This way applications that can > > generate complex packets can verify that the device will be able to > > process them, and applications that only generate simple mbufs can avoid > > the overhead by not calling the function. > > More than a check, it should be exposed as a capability of the port. > Anyway, if the application sends too much segments, the driver must > drop it to avoid hang, and maintain a dedicated statistic counter to allow > easy debugging. I agree with Thomas - this should not be optional. Malformed packets should be dropped. In the icgbe case it's a very simple test - it's a single branch per packet so i doubt that it could impose any measurable performance degradation. >