From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <harry.van.haaren@intel.com> Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by dpdk.org (Postfix) with ESMTP id 795D58D28 for <dev@dpdk.org>; Tue, 9 Feb 2016 16:20:06 +0100 (CET) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP; 09 Feb 2016 07:20:05 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,421,1449561600"; d="scan'208";a="899387660" Received: from sie-lab-212-120.ir.intel.com (HELO silpixa00394367.ir.intel.com) ([10.237.212.120]) by fmsmga001.fm.intel.com with ESMTP; 09 Feb 2016 07:20:04 -0800 From: Harry van Haaren <harry.van.haaren@intel.com> To: jing.d.chen@intel.com Date: Tue, 9 Feb 2016 15:19:54 +0000 Message-Id: <1455031194-27921-1-git-send-email-harry.van.haaren@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1454946137-5505-1-git-send-email-harry.van.haaren@intel.com> References: <1454946137-5505-1-git-send-email-harry.van.haaren@intel.com> Cc: dev@dpdk.org Subject: [dpdk-dev] [PATCH v2] docs: add statistics read frequency to fm10k guide X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Tue, 09 Feb 2016 15:20:06 -0000 This patch documents that the statistics of fm10k based NICs must be read regularly in order to avoid an undetected 32 bit integer-overflow. Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com> --- v2: -Moved notes to Known Issues section of Release Notes. doc/guides/nics/fm10k.rst | 16 ++++++++++++++++ doc/guides/rel_notes/release_2_3.rst | 4 ++++ 2 files changed, 20 insertions(+) diff --git a/doc/guides/nics/fm10k.rst b/doc/guides/nics/fm10k.rst index 4206b7f..4250c9e 100644 --- a/doc/guides/nics/fm10k.rst +++ b/doc/guides/nics/fm10k.rst @@ -65,3 +65,19 @@ The FM10000 family of NICS support a maximum of a 15K jumbo frame. The value is fixed and cannot be changed. So, even when the ``rxmode.max_rx_pkt_len`` member of ``struct rte_eth_conf`` is set to a value lower than 15364, frames up to 15364 bytes can still reach the host interface. + +Statistic Polling Frequency +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The FM10000 NICs expose a set of statistics via the PCI BARs. These statistics +are read from the hardware registers when ``rte_eth_stats_get()`` or +``rte_eth_xstats_get()`` is called. The packet counting registers are 32 bits +while the byte counting registers are 48 bits. As a result, the statistics must +be polled regularly in order to ensure the consistency of the returned reads. + +Given the PCIe Gen3 x8, about 50Gbps of traffic can occur. With 64 byte packets +this gives almost 100 million packets/second, causing 32 bit integer overflow +after approx 40 seconds. To ensure these overflows are detected and accounted +for in the statistics, it is necessary to read statistic regularly. It is +suggested to read stats every 20 seconds, which will gaurantee the statistics +are accurate. diff --git a/doc/guides/rel_notes/release_2_3.rst b/doc/guides/rel_notes/release_2_3.rst index 99de186..6748b89 100644 --- a/doc/guides/rel_notes/release_2_3.rst +++ b/doc/guides/rel_notes/release_2_3.rst @@ -31,6 +31,10 @@ Other Known Issues ------------ +* **FM10K: Statistics Polling Frequency** + + A section has been added to the NIC guide for fm10k about the maximum + time between reading statistics and 32 bit packet counter overflows. API Changes ----------- -- 2.5.0