Why the trigered counts of NMIs is equivalent to PMI's?

[孙世龙 sunshilong]

As the subject, here is the statics got from my PC at a different time:
 $cat /proc/interrupts | grep -E 'NMI|PMI'
 NMI:        649        374        347        424   Non-maskable interrupts
 PMI:        649        374        347        424   Performance
monitoring interrupts

$ cat /proc/interrupts | grep -Ei 'PMI|NMI'
 NMI:        247        274        238        289   Non-maskable interrupts
 PMI:        247        274        238        289   Performance
monitoring interrupts