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diff --git a/docs/userguide/low_latency.userguide.rst b/docs/userguide/low_latency.userguide.rst new file mode 100644 index 000000000..e0d2791df --- /dev/null +++ b/docs/userguide/low_latency.userguide.rst @@ -0,0 +1,68 @@ +.. 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 `tuning.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. |