On Tue, Mar 29, 2016 at 09:31:58AM +0200, Peter Zijlstra wrote:
> This will not in fact work for Intel, nor if I manage to one day
> randomize our CPU numbers on AMD.
Oh, I know why. I have this 64 CPUs box here:
$ grep "core id" /proc/cpuinfo | uniq
core id : 0
core id : 8
core id : 2
core id : 10
core id : 1
core id : 9
core id : 3
core id : 11
core id : 0
core id : 8
core id : 2
core id : 10
core id : 1
core id : 9
core id : 3
core id : 11
Those core IDs repeat and are almost random too :)
I guess we'll need a mask. Maybe as a future exercise...
That box's topology has other funsies like this:
$ grep -E -B 2 "core id\s+: 0" /proc/cpuinfo
physical id : 0
siblings : 16
core id : 0
--
physical id : 1
siblings : 16
core id : 0
--
physical id : 2
siblings : 16
core id : 0
--
physical id : 3
siblings : 16
core id : 0
--
physical id : 0
siblings : 16
core id : 0
--
physical id : 1
siblings : 16
core id : 0
--
physical id : 2
siblings : 16
core id : 0
--
physical id : 3
siblings : 16
core id : 0
So in order to dig out which HT threads belong together, I need to look
at the (core id, physical id) pair.
I guess this is how we "fix" the schedulers of other OSes - by playing
topology games...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
