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.\" Copyright (c) 2015 Mark Johnston <markj@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd April 18, 2015
.Dt DTRACE_IO 4
.Os
.Sh NAME
.Nm dtrace_io
.Nd a DTrace provider for tracing events related to disk I/O
.Sh SYNOPSIS
.Fn io:::start "struct bio *" "struct devstat *"
.Fn io:::done "struct bio *" "struct devstat *"
.Sh DESCRIPTION
The
.Nm 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
.Xr disk 9
object.
This occurs after all
.Xr 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
.Xr disk 9
object.
.Sh ARGUMENTS
The fields of
.Vt "struct bio"
are described in the
.Xr g_bio 9
manual page, and the fields of
.Vt "struct devstat"
are described in the
.Xr devstat 9
manual page.
Translators for the
.Vt bufinfo_t
and
.Vt devinfo_t
D types are defined in
.Pa /usr/lib/dtrace/io.d .
.Sh FILES
.Bl -tag -width "/usr/lib/dtrace/io.d" -compact
.It Pa /usr/lib/dtrace/io.d
DTrace type and translator definitions for the
.Nm io
provider.
.El
.Sh EXAMPLES
The following script shows a per-process breakdown of total I/O by disk device:
.Bd -literal -offset indent
#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", @);
}
.Ed
.Sh COMPATIBILITY
This provider is not compatible with the
.Nm io
provider found in Solaris, as its probes use native
.Fx
argument types.
.Sh SEE ALSO
.Xr dtrace 1 ,
.Xr devstat 9 ,
.Xr SDT 9
.Sh HISTORY
The
.Nm io
provider first appeared in
.Fx
9.2 and 10.0.
.Sh AUTHORS
This manual page was written by
.An Mark Johnston Aq Mt markj@FreeBSD.org .
.Sh BUGS
The
.Fn io:::wait-start
and
.Fn io:::wait-done
probes are not currently implemented on
.Fx .
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