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T3048: add documentation for "system options performance" command

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Christian Poessinger 2020-11-12 18:22:11 +01:00
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commit 85206b1c28
2 changed files with 43 additions and 3 deletions
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docs/system/advanced-index.rst
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.. _advanced_system_tweaks:
######################
Advanced System Tweaks
######################
######
System
######
.. toctree::
:maxdepth: 2
@ -11,6 +11,7 @@ Advanced System Tweaks
flow-accounting
ntp
options
options-performance
boot-options
proxy
serial-console

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.. _system_options_performance:
###########
Performance
###########
As more and more routers run on Hypervisors, expecially with a :abbr:`NOS
(Network Operating System)` as VyOS, it makes fewer and fewer sense to use
static resource bindings like ``smp-affinity`` as present in VyOS 1.2 and
earlier to pin certain interrupt handlers to specific CPUs.
We now utilize `tuned` for dynamic resource balancing based on profiles.
.. seealso:: https://access.redhat.com/sites/default/files/attachments/201501-perf-brief-low-latency-tuning-rhel7-v2.1.pdf
Configureation
==============
.. cfgcmd:: set system options performance < throughput | latency >
Configure one of the predefined system performance profiles.
* ``throughput``: A server profile focused on improving network throughput.
This profile favors performance over power savings by setting ``intel_pstate``
and ``max_perf_pct=100`` and increasing kernel network buffer sizes.
It enables transparent huge pages, and uses cpupower to set the performance
cpufreq governor. It also sets ``kernel.sched_min_granularity_ns`` to 10 us,
``kernel.sched_wakeup_granularity_ns`` to 15 uss, and ``vm.dirty_ratio`` to
40%.
* ``latency``: A server profile focused on lowering network latency.
This profile favors performance over power savings by setting ``intel_pstate``
and ``min_perf_pct=100``.
It disables transparent huge pages, and automatic NUMA balancing. It also
uses cpupower to set the performance cpufreq governor, and requests a
cpu_dma_latency value of 1. It also sets busy_read and busy_poll times to
50 us, and tcp_fastopen to 3.