On Fri, 11 Mar 2016, Luck, Tony wrote:
> With this patch applied my system survives me doing
> several rounds of:
>
> # echo 0 | tee /sys/devices/system/cpu/cpu*/online
> # echo 1 | tee /sys/devices/system/cpu/cpu*/online
>
> whereas without the patch the first of those went to
>
> [152455.129604] NMI watchdog: Watchdog detected hard LOCKUP on cpu 96
> [152455.136943] Kernel panic - not syncing: Hard LOCKUP
>
> I'm not sure we care to optimize the cpu offline path, but I'll note here
> that taking all (but one) cpus offline took 52 seconds (for a hundred
> and mumble logical cpus). Bringing them all back is just 4 seconds.
Yes. I noticed that as well. No idea where we waste all that time. I've put
that on the todo list of our ongoing hotplug refactoring work.
Thanks,
tglx
