11.9.1 io Probes

The following table describes the probes for the io provider.

Table 11.9 io Probes

Probe

Description

start

Fires when an I/O request is about to be made either to a peripheral device or to an NFS server.

done

Fires after an I/O request has been fulfilled. The done probe fires after the I/O completes, but before completion processing has been performed on the buffer. As a result B_DONE is not set in b_flags at the time the done probe fires.

wait-start

Fires immediately before a thread begins to wait pending completion of a given I/O request. Some time after the wait-start probe fires, the wait-done probe fires in the same thread.

wait-done

Fires when a thread finishes waiting for the completion of a given I/O request. The wait-done probe fires only after the wait-start probe has fired in the same thread.


The io probes fire for all I/O requests to peripheral devices, and for all file read and file write requests to an NFS server. Requests for metadata from an NFS server, for example, do not trigger io probes due to a readdir() request.