NAME

       dtrace_io — a DTrace provider for tracing events related to disk I/O

SYNOPSIS

       io:::start(struct bio *, struct devstat *);

       io:::done(struct bio *, struct devstat *);

DESCRIPTION

       The  io  provider allows the tracing of disk I/O events.  The io:::start() probe fires when a I/O request
       is about to be sent to  the  backing  driver  of  a  disk(9)  object.   This  occurs  after  all  GEOM(4)
       transformations  have  been  performed on the request.  The io:::done() probe fires when a I/O request is
       completed.  Both probes take a struct bio * representing the I/O request as their  first  argument.   The
       second argument is a struct devstat * for the underlying disk(9) object.

ARGUMENTS

       The  fields of struct bio are described in the g_bio(9) manual page, and the fields of struct devstat are
       described in the devstat(9) manual page.  Translators for the bufinfo_t and devinfo_t D types are defined
       in /usr/lib/dtrace/io.d.

FILES

       /usr/lib/dtrace/io.d  DTrace type and translator definitions for the io provider.

EXAMPLES

       The following script shows a per-process breakdown of total I/O by disk device:

             #pragma D option quiet

             io:::start
             {
                     @[args[1]->device_name, execname, pid] = sum(args[0]->bio_bcount);
             }

             END
             {
                     printf("%10s %20s %10s %15s\n", "DEVICE", "APP", "PID", "BYTES");
                     printa("%10s %20s %10d %15@d\n", @);
             }

COMPATIBILITY

       This provider is not compatible with the io provider found in Solaris, as its probes use  native  FreeBSD
       argument types.

SEE ALSO

       dtrace(1), devstat(9), SDT(9)

HISTORY

       The io provider first appeared in FreeBSD 9.2 and 10.0.

AUTHORS

       This manual page was written by Mark Johnston <markj@FreeBSD.org>.

BUGS

       The io:::wait-start() and io:::wait-done() probes are not currently implemented on FreeBSD.

Debian                                           April 18, 2015                                     DTRACE_IO(4)