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authorJiang, Yunhong <yunhong.jiang@intel.com>2016-08-19 22:38:30 +0000
committerGerrit Code Review <gerrit@172.30.200.206>2016-08-19 22:38:30 +0000
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tree13d77cab75c7aebcfd88988e1c104188472e2e6f /docs/userguide/low_latency.userguide.rst
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parent5a56bf69988b7c72e88546eb4659576fb51bfb77 (diff)
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+.. This work is licensed under a Creative Commons Attribution 4.0 International License.
+
+.. http://creativecommons.org/licenses/by/4.0
+
+Low Latency Environment
+=======================
+
+Achieving low latency with the KVM4NFV project requires setting up a special
+test environment. This environment includes the BIOS settings, kernel
+configuration, kernel parameters and the run-time environment.
+
+Hardware Environment Description
+--------------------------------
+
+BIOS setup plays an important role in achieving real-time latency. A collection
+of relevant settings, used on the platform where the baseline performance data
+was collected, is detailed below:
+
+CPU Features
+~~~~~~~~~~~~
+
+Some special CPU features like TSC-deadline timer, invariant TSC and Process
+posted interrupts, etc, are helpful for latency reduction.
+
+CPU Topology
+~~~~~~~~~~~~
+
+NUMA topology is also important for latency reduction.
+
+BIOS Setup
+~~~~~~~~~~
+
+Careful BIOS setup is important in achieving real time latency. Different
+platforms have different BIOS setups, below are the important BIOS settings on
+the platform used to collect the baseline performance data.
+
+Software Environment Setup
+--------------------------
+Both the host and the guest environment need to be configured properly to
+reduce latency variations. Below are some suggested kernel configurations.
+The ci/envs/ directory gives detailed implementation on how to setup the
+environment.
+
+Kernel Parameter
+~~~~~~~~~~~~~~~~
+
+Please check the default kernel configuration in the source code at:
+kernel/arch/x86/configs/opnfv.config.
+
+Below is host kernel boot line example:
+::
+isolcpus=11-15,31-35 nohz_full=11-15,31-35 rcu_nocbs=11-15,31-35
+iommu=pt intel_iommu=on default_hugepagesz=1G hugepagesz=1G mce=off idle=poll
+intel_pstate=disable processor.max_cstate=1 pcie_asmp=off tsc=reliable
+
+Below is guest kernel boot line example
+::
+isolcpus=1 nohz_full=1 rcu_nocbs=1 mce=off idle=poll default_hugepagesz=1G
+hugepagesz=1G
+
+Please refer to `tunning.userguide` for more explanation.
+
+Run-time Environment Setup
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Not only are special kernel parameters needed but a special run-time
+environment is also required. Please refer to `tunning.userguide` for
+more explanation.