Erlang can't retrieve count of CPU cores

[tomp (Thomas Parrott)]

I wonder if perhaps related to:

Online cpu numbers in /sys/devices/system/cpu/online and sched_getaffinity masks

I just wasted two days debugging a java8 app, where java8 incorrectly gets a number of CPUS, it looks at /sys/devices/system/cpu/online and sched_getaffinity but that shows the host affinity maps, not the container’s, e.g. [root@int9662 ~]# fgrep -c processor /proc/cpuinfo 8 [root@int9662 ~]# cat /sys/devices/system/cpu/online 0,2,5,7,11,17,19,31 so obviously this is “impossible”, if the system has 8 cores then they are numbered 0-7, not 11,17 or whatnot, so jdk8 simply discards impossible …

CC @stgraber