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[Bug 1587265] Re: ubuntu not work with tickless kernel boot option


Did this issue start happening after an update/upgrade? Was there a
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introduced the problem.

** Changed in: linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu)
       Status: Confirmed => Incomplete

** Tags added: kernel-da-key

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  ubuntu not work with tickless kernel boot option

Status in linux package in Ubuntu:

Bug description:
  For redhat, we have such guide like 

  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_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash isolcpus=1-2 nohz_full=1-2"

  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.

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