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View Full Version : Page faults - what are they? Is 926,618 page faults normal?


bluehz
06-14-2003, 10:16 AM
I use MenuMeters and while I understand they may not be the most accurate guage - they do give me a nice quick peek at whats going on. Recently I have been watching teh VM Statistic and they worry me a bit. The following statistics are taken immediately after a startup.

Does this seem normal to have that many page faults and cache lookups?
Memory Usage:
220.1MB used, 931.9MB free, 1,152.0MB total

Memory Pages:
132.6MB active, 87.6MB wired
299.7MB inactive, 632.2MB free

VM Statistics:
10,861 pageins, 2 pageouts
27,551 cache lookups, 18,241 cache hits (66.2%)
926,618 page faults, 39,504 copy-on-writes

Swap Files:
1 swap present
76.3MB total swap space

mervTormel
06-14-2003, 10:47 AM
menuMeters is reporting "translation faults" as page faults, a bit misleading, but you'll have to read up on VM mechanisms:

$ vm_stat
Mach Virtual Memory Statistics: (page size of 4096 bytes)
Pages free: 251455.
Pages active: 86434.
Pages inactive: 27404.
Pages wired down: 27923.
"Translation faults": 41730198.
Pages copy-on-write: 383226.
Pages zero filled: 32515690.
Pages reactivated: 69178.
Pageins: 58263.
Pageouts: 2276.
Object cache: 115735 hits of 2632113 lookups (4% hit rate)

man vm_stat
...
Translation faults
the number of times the "vm_fault" routine has been called.
...

a very high number of t-faults is normal. there are soft faults and hard faults. pageouts are hard.