dtrace_io (4)

Leading comments

Copyright (c) 2015 Mark Johnston <markj@FreeBSD.org>
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(The comments found at the beginning of the groff file "man4/dtrace_io.4freebsd".)

NAME

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

SYNOPSIS

Fn io:::start struct bio * struct devstat * Fn io:::done struct bio * struct devstat *

DESCRIPTION

The io provider allows the tracing of disk I/O events. The Fn 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 Fn io:::done probe fires when a I/O request is completed. Both probes take a Vt struct bio * representing the I/O request as their first argument. The second argument is a Vt struct devstat * for the underlying disk(9) object.

ARGUMENTS

The fields of Vt struct bio are described in the g_bio9 manual page, and the fields of Vt struct devstat are described in the devstat(9) manual page. Translators for the Vt bufinfo_t and Vt 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 Fx argument types.

SEE ALSO

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

HISTORY

The io provider first appeared in Fx 9.2 and 10.0.

AUTHORS

This manual page was written by An Mark Johnston Aq Mt markj@FreeBSD.org .

BUGS

The Fn io:::wait-start and Fn io:::wait-done probes are not currently implemented on Fx .