Page Faults

Page fault probes relate virtual addresses with fault types and with files (vnodes).

The address_fault probe traces address-space faults; it records the faulting virtual address, the type of fault, and the desired access protection.

The fault type and access type values use the constants defined in <vm/seg_enum.h>. Fault types are invalid page (minor fault), protection fault, or software requests to lock and unlock pages for physical I/O (softlock and softunlock). Access types are read, write, execute and create.

The major_fault probe traces major page faults; it records the vnode and offset (which together identify a file system page) from which the fault should be resolved. This data can be correlated with the immediately preceding address_fault event for the current thread to obtain the faulting virtual address.

The anon_private probe traces copy-on-write faults.

The anon_zero probe traces zero-fill faults.

The page_unmap probe marks the dissociation between a physical page and a file system page (for example, when a page is renamed or destroyed).