Cpu core number != CPU_allows , why?

Question

 **cpu :** E5-2630L * 2 
 **os :** Linux CentOS 6.3

physical core : 12
logical core : 24 (grep -c processor /proc/cpuinfo, by hyper threading)

 E5-2630L has 6 cores, so total 24. (6*2*2)
 but /proc/pid/status is

  - Cpus_allowed:   ffffffff,ffffffff
  - Cpus_allowed_list:      0-63

cpu has 24 logical cores, but why cpu_allowed is 64?

Answer 1

It is the default, it just means there is no further restriction (besides the available hardware). I think the mask is a multiple of 32bit, but it always starts with 2 times that.