This is still the case in Ubuntu 20.04: $ cat /boot/config-5.11.0-27-generic | grep HZ_FULL # CONFIG_NO_HZ_FULL is not set
This is problematic insofar as HZ_FULL is apparently useful for reliable benchmarking (e.g. see https://vstinner.github.io/journey-to-stable- benchmark-system.html). Would be nice to get this fixed! -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1587265 Title: ubuntu not work with tickless kernel boot option Status in linux package in Ubuntu: Confirmed Bug description: 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. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1587265/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
