I've been testing this stuff trying to reserve some CPUs in a host with two Intel E5645 but I can't get it working for some reason. Steps I followed:
-
Edit /etc/default/grub and added isolcpus=0,1 to GRUB_CMDLINE_LINUX_DEFAULT
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash isolcpus=0,1"
-
Run update-grub
- Reboot
After that, cat /proc/cmdline reveals:
BOOT_IMAGE=/boot/vmlinuz-3.2.0-26-generic root=UUID=52cfedad-40be-41b9-9f88-c282a7ae3f24 ro quiet splash isolcpus=0,1 vt.handoff=7
Tested using stress:
apt-get install stress && stress -c 24
Monitored using top and pressing 1 to display individual CPU stats. So far no CPUs are isolated from the scheduler and all of them are busted by stress.
Cpu0 : 99.7%us, 0.3%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu1 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu2 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu3 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu4 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu5 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu6 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu7 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu8 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu9 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu10 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu11 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu12 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu13 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu14 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu15 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu16 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu17 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu18 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu19 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu20 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu21 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu22 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Cpu23 :100.0%us, 0.0%sy, 0.0%ni, 0.0%id, 0.0%wa
Tested the same stuff in CentOS 6 x86_64 and it works as expected.
Searched ubuntu and linux bugs database in launchpad but did not find anything so far.
Is it me being dumb or am I missing something? Hints?
Thanks!
Refs:
http://www.kernel.org/doc/Documentation/kernel-parameters.txt
Best Answer
Disabled SMT (Hyper-Threading) in BIOS, power cycled, tested again with HT off and isolcpus works as expected.
Re-enabled SMT in BIOS, power cycled, still works as expected.
Definitely not the best answer you could expect, but it worked for me nevertheless.