From owner-freebsd-net@FreeBSD.ORG Tue May 8 04:56:01 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E0FF1106574C for ; Tue, 8 May 2012 04:56:01 +0000 (UTC) (envelope-from juli@clockworksquid.com) Received: from mail-we0-f182.google.com (mail-we0-f182.google.com [74.125.82.182]) by mx1.freebsd.org (Postfix) with ESMTP id 6374C8FC16 for ; Tue, 8 May 2012 04:56:01 +0000 (UTC) Received: by werg1 with SMTP id g1so966780wer.13 for ; Mon, 07 May 2012 21:56:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type :x-gm-message-state; bh=X2XRl/dNeh1gVGjH8R0m9hDnIgnprefuX3FMBbrQrqc=; b=O0nsr6I8oL2gRRUAPVLq0Wp0aGIOzhSn9zCZ+DeTFejsqypb8itGn6v5kY4orTu3t0 IUsDqrHitKVSscefKuztwr8I5yLI1bW3a4Y5Ulw8l2+lXL+6dMSAbcdTNMfVSgcgkYiP Ls2SI9kMZuUL0oKbg3GYlCztB6nVbXrN+WNVYOa+eD5SKPh+7cGMd8cVVwFrD9Pqkg4+ p8eGFsrwxw977TWUbEWu/vhJO2duKSe8jxyuMczQoPPrtBxVPpLiKZ228veTiE0ciWp/ LVqtRYTOzbvpVVGRIBaDSmHmnMsJAx6eRAEoEWQ+F4pXG37pY+W+LR+7dDxl+Ktssc8K l9Tw== Received: by 10.180.80.104 with SMTP id q8mr41072626wix.14.1336452960162; Mon, 07 May 2012 21:56:00 -0700 (PDT) MIME-Version: 1.0 Sender: juli@clockworksquid.com Received: by 10.180.146.169 with HTTP; Mon, 7 May 2012 21:55:39 -0700 (PDT) In-Reply-To: References: From: Juli Mallett Date: Mon, 7 May 2012 21:55:39 -0700 X-Google-Sender-Auth: iVIMXiBWjGlRyf6Mksyd56pU1tI Message-ID: To: Vijay Singh Content-Type: text/plain; charset=UTF-8 X-Gm-Message-State: ALoCoQmGcsnJO7nJYsw0+TOCFaA6mmKTdkjwKafHABMRzopGBwMQlQdoK39QHyJV/agN0O9Qqwoq Cc: freebsd-net@freebsd.org, Jack Vogel Subject: Re: What does adapter->stats.mpc[] report for ixgbe? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 May 2012 04:56:02 -0000 On Mon, May 7, 2012 at 9:42 PM, Vijay Singh wrote: >> normal net traffic. But for now in FreeBSD its just one which is divided >> into 3 parts: TX, RX, and FDIR (flow director). > > Jack, does the sw driver control in any way the partitioning of the > FIFO? I guess enabling 2 hw queues splits the FIFO in half. But > otherwise does the driver control this in any way? I don't believe that multiple queues splits the FIFO (Jack can correct me if I'm wrong.) This is a small (very small) chunk of low-latency memory on the NIC itself that is used to store the packets as they come in off the wire before they are moved to a receive descriptor. The driver does have a way of partitioning the space between transmit and receive, look for "PBA" in the drivers. In some cases if you're doing mostly-transmit or mostly-receive it can be very helpful to tweak these values, but in the case where you're running out of receive FIFO space constantly, it's (in my limited experience) more likely to be a problem with bandwidth or latency between the NIC and main memory, causing backpressure within the NIC as it tries to move packets to receive buffers (which are the ones allocated in main, i.e. host, memory.)