openstack/octavia
Code Issues Proposed changes

Set nohz_full in cpu-pinning element

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nohz_full (or full dynticks) is a Linux kernel setting that should reduce
kernel noise on configured CPUs to a minimum. This change activates this
setting on all vCPUs except the first one.

Change-Id: Ie009aff52d572873da0bb5cc43fedd7f3325dccc
This commit is contained in:
Tom Weininger 2022-08-19 11:00:31 +02:00
parent 0b1b6c58f5
commit baefc3b464
2 changed files with 14 additions and 0 deletions
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1
elements/cpu-pinning/environment.d/80-kernel-cpu-affinity
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@ -27,6 +27,7 @@ case $DISTRO_NAME in
DIB_BOOTLOADER_DEFAULT_CMDLINE+=" irqaffinity=0"
# This will be ignored on single vCPU systems
DIB_BOOTLOADER_DEFAULT_CMDLINE+=" isolcpus=1-N"
DIB_BOOTLOADER_DEFAULT_CMDLINE+=" nohz=on nohz_full=1-N"
export DIB_BOOTLOADER_DEFAULT_CMDLINE
;;
*)

13
releasenotes/notes/use-nohz-full-to-improve-latency-9d5acd7333f7e462.yaml Normal file
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@ -0,0 +1,13 @@
---
features:
- |
The cpu-pinning element for the amphora image sets the kernel bootarg
nohz_full=1-N to enable
full dynticks on all CPUs except the first one (on single CPU images this
will have no effect). This should reduce kernel noise on those CPUs to a
minimum and reduce latency.
upgrade:
- |
In order for the full dynticks optimization to become effective a new
amphora image needs to be built with the new optional CPU pinning
feature enabled.