From patchwork Sun Jul 2 12:06:44 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qi Zhang X-Patchwork-Id: 26181 X-Patchwork-Delegate: thomas@monjalon.net Return-Path: X-Original-To: patchwork@dpdk.org Delivered-To: patchwork@dpdk.org Received: from [92.243.14.124] (localhost [IPv6:::1]) by dpdk.org (Postfix) with ESMTP id 068D937B0; Sun, 2 Jul 2017 13:16:21 +0200 (CEST) Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id CF58437A8 for ; Sun, 2 Jul 2017 13:16:18 +0200 (CEST) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP; 02 Jul 2017 04:16:17 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.40,297,1496127600"; d="scan'208";a="106220982" Received: from dpdk23.sh.intel.com ([10.67.111.80]) by orsmga002.jf.intel.com with ESMTP; 02 Jul 2017 04:16:16 -0700 From: Qi Zhang To: john.mcnamara@intel.com, jingjing.wu@intel.com Cc: helin.zhang@intel.com, dev@dpdk.org, Qi Zhang Date: Sun, 2 Jul 2017 08:06:44 -0400 Message-Id: <20170702120644.3510-1-qi.z.zhang@intel.com> X-Mailer: git-send-email 2.9.3 Subject: [dpdk-dev] [PATCH] doc: add knowing issue for i40e VF performance X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" VF performance is limited by some kernel PCI setting. Update the document to explain the knowing issue and work around solution. Signed-off-by: Qi Zhang --- doc/guides/nics/i40e.rst | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst index 4d3c7ca..557d83d 100644 --- a/doc/guides/nics/i40e.rst +++ b/doc/guides/nics/i40e.rst @@ -447,3 +447,27 @@ It means if APP has set the max bandwidth for that TC, it comes to no effect. It's suggested to set the strict priority mode for a TC that is latency sensitive but no consuming much bandwidth. + +VF performance is impacted by PCI extended tag setting +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To reach maximum NIC performance. PCI extended tag is required to be enabled. +DPDK I40E PF drvier will set this feature during initialization, but Kernel PF +driver does not. So when running traffic on a VF which is managed by kernel +PF driver, we saw significent NIC performance downgrade (for 64 bytes packet, +there is about 25% linerate downgrade for 25G device and about 35% for 40G +device). + +Solution: + +For kernel version >= 4.11, kernel's PCI driver will enale extended tag if it +detects that device support extended tag. So by default, this is not an issue. +When extended tag is be disabled by occasionally, to re-enable it, see below. + +For kernel version < 4.11, use setpci command to enable PCI extended flag +1) get current value of PCI configure register +setpci -s a8.w +2) set bit 8 +value = value | 0x100 +3) set PCI configure register with new value. +setpci -s a8.w=