Public bug reported:
For redhat, we have such guide like
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/pdf/Performance_Tuning_Guide/Red_Hat_Enterprise_Linux-7-Performance_Tuning_Guide-en-US.pdf
and for tickless kernel, (use dynamic tickless ways)
1. config grub with following cmdline
$ cat /etc/default/grub
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'
GRUB_DEFAULT=0
GRUB_HIDDEN_TIMEOUT=0
GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash isolcpus=1-2 nohz_full=1-2"
GRUB_CMDLINE_LINUX=""
I used nohz_full here, and it is CPU 1, 2 here.
2. update-grub after that.
3. Then reboot system
4. execute following
$ sudo perf stat -C 1 -e irq_vectors:local_timer_entry taskset -c 1 stress
-t 1 -c 1
stress: info: [3869] dispatching hogs: 1 cpu, 0 io, 0 vm, 0 hdd
stress: info: [3869] successful run completed in 1s
Performance counter stats for 'CPU(s) 1':
252 irq_vectors:local_timer_entry
1.001491203 seconds time elapsed
It always 252, (the default 250 HZ), seems tickless kernel option not have any
effect, whether config it or not, both have same results.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: Incomplete
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https://bugs.launchpad.net/bugs/1587265
Title:
ubuntu not work with tickless kernel boot option
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