Solaris Dynamic Tracing Guide

Probes

The io probes are described in Table 27–1.

Table 27–1 io Probes


Probe	Description
`start`	Probe that fires when an I/O request is about to be made either to a peripheral device or to an NFS server. The `bufinfo_t` corresponding to the I/O request is pointed to by `args[0]`. The `devinfo_t` of the device to which the I/O is being issued is pointed to by `args[1]`. The `fileinfo_t` of the file that corresponds to the I/O request is pointed to by `args[2]`. Note that file information availability depends on the filesystem making the I/O request. See `fileinfo_t` for more information.
`done`	Probe that fires after an I/O request has been fulfilled. The `bufinfo_t` corresponding to the I/O request is pointed to by `args[0]`. 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. The `devinfo_t` of the device to which the I/O was issued is pointed to by `args[1]`. The `fileinfo_t` of the file that corresponds to the I/O request is pointed to by `args[2]`.
`wait-start`	Probe that fires immediately before a thread begins to wait pending completion of a given I/O request. The buf(9S) structure corresponding to the I/O request for which the thread will wait is pointed to by `args[0]`. The `devinfo_t` of the device to which the I/O was issued is pointed to by `args[1]`. The `fileinfo_t` of the file that corresponds to the I/O request is pointed to by `args[2]`. Some time after the `wait-start` probe fires, the `wait-done` probe will fire in the same thread.
`wait-done`	Probe that fires when a thread is done waiting for the completion of a given I/O request. The `bufinfo_t` corresponding to the I/O request for which the thread will wait is pointed to by `args[0]`. The `devinfo_t` of the device to which the I/O was issued is pointed to by `args[1]`. The `fileinfo_t` of the file that corresponds to the I/O request is pointed to by `args[2]`. The `wait-done` probe fires only after the `wait-start` probe has fired in the same thread.

Note that 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(3C) request.