Device statistics library. Used by iostat, vmstat, and systat to

format and analyze the output of the new device statistics sysctls.

Submitted by:	"Kenneth D. Merry" <ken@FreeBSD.org>

4 files changed, 1755 insertions, 0 deletions

diff --git a/lib/libdevstat/Makefile b/lib/libdevstat/Makefile
new file mode 100644
index 0000000..ce3f9c2
--- /dev/null
+++ b/lib/libdevstat/Makefile
@@ -0,0 +1,13 @@
+
+LIB=	devstat
+SRCS=	devstat.c
+
+MAN3=	devstat.3
+
+beforeinstall:
+	${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 ${.CURDIR}/devstat.h \
+	    ${DESTDIR}/usr/include
+
+CFLAGS+=-I${.CURDIR} -I${.CURDIR}/../../sys
+
+.include <bsd.lib.mk>
diff --git a/lib/libdevstat/devstat.3 b/lib/libdevstat/devstat.3
new file mode 100644
index 0000000..189f703
--- /dev/null
+++ b/lib/libdevstat/devstat.3
@@ -0,0 +1,525 @@
+.\"
+.\" Copyright (c) 1998 Kenneth D. Merry.
+.\" 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.
+.\" 3. The name of the author may not be used to endorse or promote products
+.\"    derived from this software without specific prior written permission.
+.\"
+.\" 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.
+.\"
+.\"	$Id$
+.\"
+.Dd May 21, 1998
+.Dt DEVSTAT 3
+.Os FreeBSD 3.0
+.Sh NAME
+.Nm devstat
+.Nd device statistics utility library
+.Sh SYNOPSIS
+.Fd #include <devstat.h>
+.Ft int
+.Fn getnumdevs "void"
+.Ft int
+.Fn getgeneration "void"
+.Ft int
+.Fn getversion "void"
+.Ft int
+.Fn checkversion "void"
+.Ft int
+.Fn getdevs "struct statinfo *stats"
+.Ft int
+.Fo selectdevs
+.Fa "struct device_selection **dev_select"
+.Fa "int *num_selected"
+.Fa "int *num_selections"
+.Fa "int *select_generation"
+.Fa "int current_generation"
+.Fa "struct devstat *devices"
+.Fa "int numdevs"
+.Fa "struct devstat_match *matches"
+.Fa "int num_matches"
+.Fa "char **dev_selections"
+.Fa "int num_dev_selections"
+.Fa "devstat_select_mode select_mode"
+.Fa "int maxshowdevs"
+.Fa "int perf_select"
+.Fc
+.Ft int
+.Fo buildmatch
+.Fa "char *match_str"
+.Fa "struct devstat_match **matches"
+.Fa "int *num_matches"
+.Fc
+.Ft int
+.Fo compute_stats
+.Fa "struct devstat *current"
+.Fa "struct devstat *previous"
+.Fa "long double etime"
+.Fa "u_int64_t *total_bytes"
+.Fa "u_int64_t *total_transfers"
+.Fa "u_int64_t *total_blocks"
+.Fa "long double *kb_per_transfer"
+.Fa "long double *transfers_per_second"
+.Fa "long double *mb_per_second"
+.Fa "long double *blocks_per_second"
+.Fa "long double *ms_per_transaction"
+.Fc
+.Ft long double
+.Fo compute_etime
+.Fa "struct timeval cur_time"
+.Fa "struct timeval prev_time"
+.Fc
+.Sh DESCRIPTION
+The
+.Nm
+library is a library of helper functions for dealing with the kernel
+.Xr devstat 9
+interface, which is accessible to users via
+.Xr sysctl 3 .
+.Pp
+.Fn getnumdevs
+returns the number of devices registered with the
+.Nm devstat
+subsystem in the kernel.
+.Pp
+.Fn getgeneration
+returns the current generation of the
+.Nm devstat
+list of devices in the kernel.
+.Pp
+.Fn getversion
+returns the current kernel
+.Nm devstat
+version.
+.Pp
+.Fn checkversion
+checks the userland devstat version against the kernel devstat version.  If
+the two are identical, it returns zero.  Otherwise, it prints an
+appropriate error in 
+.Va devstat_errbuf
+and returns -1.
+.Pp
+.Fn getdevs
+fetches the current list of devices and statistics into the supplied
+.Va statinfo
+structure.  The
+.Va statinfo
+structure can be found in 
+.Aq Pa devstat.h :
+.Bd -literal -offset indent
+struct statinfo {
+	long            cp_time[CPUSTATES];
+	long            tk_nin;  
+	long            tk_nout;
+	struct devinfo  *dinfo;
+	struct timeval  busy_time;
+};
+.Ed
+.Pp
+.Fn getdevs
+expects the
+.Va statinfo
+structure to be allocated, and it also expects the
+.Va dinfo
+subelement to be allocated ahead of time.  The
+.Va dinfo
+subelement contains the following elements:
+.Bd -literal -offset indent
+struct devinfo {
+	struct devstat	*devices;
+	u_int8_t	*mem_ptr;
+	int		generation;
+	int		numdevs;
+};
+.Ed
+.Pp
+The
+.Va kern.devstat.all
+.Nm sysctl
+variable contains an array of
+.Nm devstat
+structures, but at the head of the array is the current
+.Nm devstat
+generation.  The reason the generation is at the head of the buffer is so
+that userland software accessing the devstat statistics information can
+atomically get both the statistics information and the corresponding
+generation number.  If client software were forced to get the generation
+number via a separate
+.Nm sysctl
+variable (which is available for convenience), the list of devices could
+change between the time the client gets the generation and the time the
+client gets the device list.
+.Pp
+The
+.Va mem_ptr
+subelement of the
+.Va devinfo
+structure is a pointer to memory that is allocated, and resized if
+necessary, by
+.Fn getdevs .
+The devices subelement of the
+.Va devinfo
+structure is basically a pointer to the beginning of the array of devstat
+structures from the
+.Va kern.devstat.all
+.Nm sysctl
+variable.  The generation subelement of the
+.Nm devinfo
+structure contains the generation number from the
+.Va kern.devstat.all
+.Nm sysctl
+variable.  
+The
+.Va numdevs
+subelement of the 
+.Va devinfo
+structure contains the current
+number of devices registered with the kernel
+.Nm devstat
+subsystem.
+.Pp
+.Fn selectdevs
+selects devices to display based upon a number of criteria:
+.Bl -tag -width flag
+.It specified devices
+Specified devices are the first selection priority.  These are generally
+devices specified by name by the user.  e.g. da0, da1, cd0.
+.It match patterns
+These are pattern matching expressions generated by
+.Fn buildmatch
+from user input.
+.It performance
+If performance mode is enabled, devices will be sorted based on the
+.Va bytes
+field in the 
+.Va device_selection
+structure passed in to
+.Fn selectdevs .
+The 
+.Va bytes
+value currently must be maintained by the user.  In the future,
+this may be done for him in a
+.Nm
+library routine.
+If no devices have been selected by name or by pattern, the performance
+tracking code will select every device in the system, and sort them by
+perforcmance.  If devices have been selected by name or pattern, the
+performance tracking code will honor those selections and will only sort
+among the selected devices.
+.It order in the devstat list
+If the selection mode is set to DS_SELECT_ADD, and if there are still less
+than 
+.Va maxshowdevs
+devices selected,
+.Fn selectdevs
+will automatically select up to 
+.Va maxshowdevs
+devices.
+.El
+.Pp
+.Fn selectdevs
+performs selections in four different modes:
+.Bl -tag -width DS_SELECT_ADDONLY
+.It DS_SELECT_ADD
+In add mode,
+.Fn selectdevs
+will select any unselected devices specified by name or matching pattern.
+It will also select more devices, in devstat list order, until the number
+of selected devices is equal to 
+.Va maxshowdevs
+or until all devices are
+selected.
+.It DS_SELECT_ONLY
+In only mode,
+.Fn selectdevs
+will clear all current selections, and will only select devices specified
+by name or by matching pattern.
+.It DS_SELECT_REMOVE
+In remove mode,
+.Fn selectdevs
+will remove devices specified by name or by matching pattern.  It will not
+select any additional devices.
+.It DS_SELECT_ADDONLY
+In addonly mode,
+.Fn selectdevs
+will select any unselected devices specified by name or matching pattern.
+In this respect it is identical to add mode.  It will not, however, select
+any devices other than those specified.
+.El
+.Pp
+In all selection modes,
+.Fn selectdevs
+will not select any more than 
+.Va maxshowdevs
+devices.  One exception to
+this is when you are in
+.Dq top
+mode and no devices have been selected.  In
+this case,
+.Fn selectdevs
+will select every device in the system.  Client programs must pay attention
+to selection order when deciding whether to pay attention to a particular
+device.  This may be the wrong behavior, and probably requires additional
+thought.
+.Pp
+.Fn selectdevs
+handles allocation and resizing of the 
+.Va dev_select
+structure passed in
+by the client.
+.Fn selectdevs
+uses the 
+.Va numdevs
+and 
+.Va current_generation
+fields to track the
+current
+.Nm
+generation and number of devices.  If 
+.Va num_selections
+is not the same
+as 
+.Va numdevs
+or if 
+.Va select_generation
+is not the same as 
+.Va current_generation ,
+.Fn selectdevs
+will resize the selection list as necessary, and re-initialize the
+selection array.
+.Pp
+.Fn buildmatch
+takes a comma separated match string and compiles it into a
+\fBdevstat_match\fR structure that is understood by
+.Fn selectdevs .
+Match strings have the following format:
+.Pp
+.Bd -literal -offset indent
+device,type,if
+.Ed
+.Pp
+.Fn buildmatch
+takes care of allocating and reallocating the match list as necessary.
+Currently known match types include:
+.Pp
+.Bl -tag -width indent -compact
+.It device type:
+.Bl -tag -width 123456789 -compact
+.It da 
+Direct Access devices
+.It sa
+Sequential Access devices
+.It printer
+Printers
+.It proc
+Processor devices
+.It worm
+Write Once Read Multiple devices
+.It cd
+CD devices
+.It scanner
+Scanner devices
+.It optical
+Optical Memory devices
+.It changer
+Medium Changer devices
+.It comm
+Communication devices
+.It array
+Storage Array devices
+.It enclosure
+Enclosure Services devices
+.It floppy
+Floppy devices
+.El
+.Pp
+.It interface:
+.Bl -tag -width 123456789 -compact
+.It IDE
+Integrated Drive Electronics devices
+.It SCSI
+Small Computer System Interface devices
+.It other
+Any other device interface
+.El
+.Pp
+.It passthrough:
+.Bl -tag -width 123456789 -compact
+.It pass
+Passthrough devices
+.El
+.El
+.Pp
+.Fn compute_stats
+provides an easy way to obtain various device statistics.  Only two
+arguments are mandatory:
+.Va current
+and
+.Va etime .
+Every other argument is optional.  For most applications, the user will
+want to supply both
+.Va current
+and
+.Va previous
+devstat structures so that statistics may be calculated over a given period
+of time.  In some instances, for instance when calculating statistics since
+system boot, the user may pass in a NULL pointer for the
+.Va previous
+argument.  In that case,
+.Fn compute_stats
+will use the total stats in the
+.Va current
+structure to calculate statistics over
+.Va etime .
+The various statistics that may be calculated by
+.Fn compute_stats
+should be mostly explained by the function declaration itself, but for
+completeness here is a list of variable names and the statistics that will
+be put in them:
+.Bl -tag -width transfers_per_second
+.It total_bytes
+This is the total number of bytes transferred on the given device, both
+reads and writes, between the acquisition of
+.Va previous
+and the acquisition of
+.Va current .
+If
+.Va previous
+is NULL, the result will be the total reads and writes given in
+.Va current .
+.It total_transfers
+This is the total number of transfers completed between the
+acquisition of
+.Va previous
+and the acquisition of
+.Va current .
+If
+.Va previous
+is NULL, the result will be the total number of transactions listed in
+.Va current .
+.It total_blocks
+This is basically
+.Va total_bytes
+divided by the device blocksize.  If the device blocksize is listed as 
+.Sq 0 ,
+the device blocksize will default to 512 bytes.
+.It kb_per_transfer
+This is the average number of kilobytes per transfer during the measurement
+period.
+.It transfers_per_second
+This is the average number of transfers per second.
+.It mb_per_second
+This is average megabytes per second.
+.It blocks_per_second
+This is average blocks per second.  If the device blocksize is
+.Sq 0 ,
+a default blocksize of 512 bytes will be used instead.
+.It ms_per_transaction
+The average number of miliseconds per transaction.
+.El
+.Pp
+.Fn compute_etime
+provides an easy way to find the difference in seconds between two
+.Va timeval
+structures.  This is most commonly used in conjunction with the time
+recorded by the
+.Fn getdevs
+function (in struct 
+.Va statinfo )
+each time it fetches the current
+.Nm
+list.
+.Sh RETURN VALUES
+.Fn getnumdevs ,
+.Fn getgeneration ,
+and
+.Fn getversion
+return the indicated \fBsysctl\fR variable, or -1 if there is an error
+fetching the variable.
+.Pp
+.Fn checkversion
+returns 0 if the kernel and userland
+.Nm devstat
+versions match.  If they do not match, it returns -1.
+.Pp
+.Fn getdevs
+and
+.Fn selectdevs
+return -1 in case of an error, 0 if there is no error and 1 if the device
+list or selected devices have changed.  A return value of 1 from
+.Fn getdevs
+is usually a hint to re-run
+.Fn selectdevs
+because the device list has changed.
+.Pp
+.Fn buildmatch
+returns -1 for error, and 0 if there is no error.
+.Pp
+.Fn compute_stats
+returns -1 for error, and 0 for success.
+.Pp
+.Fn compute_etime
+returns the computed elapsed time.
+.Pp
+If an error is returned from one of the
+.Nm
+library functions, the reason for the error is generally printed in
+the global string
+.Va devstat_errbuf
+which is
+.Dv DEVSTAT_ERRBUF_SIZE
+characters long.
+.Sh SEE ALSO
+.Xr systat 1 ,
+.Xr iostat 8 ,
+.Xr rpc.rstatd 8 ,
+.Xr vmstat 8 ,
+.Xr devstat 9
+.Sh HISTORY
+The
+.Nm
+statistics system first appeared in
+.Fx 3.0 .
+.Sh AUTHORS
+Kenneth Merry
+.Aq ken@FreeBSD.ORG
+.Sh BUGS
+There should probably be an interface to de-allocate memory allocated by
+.Fn getdevs ,
+.Fn selectdevs ,
+and
+.Fn buildmatch .
+.Pp
+.Fn selectdevs
+should probably not select more than
+.Va maxshowdevs
+devices in
+.Dq top
+mode when no devices have been selected previously.
+.Pp
+There should probably be functions to perform the statistics buffer
+swapping that goes on in most of the clients of this library.
+.Pp
+The
+.Va statinfo
+and
+.Va devinfo
+structures should probably be cleaned up and thought out a little more.
diff --git a/lib/libdevstat/devstat.c b/lib/libdevstat/devstat.c
new file mode 100644
index 0000000..9c7828f
--- /dev/null
+++ b/lib/libdevstat/devstat.c
@@ -0,0 +1,1102 @@
+/*
+ * Copyright (c) 1997, 1998 Kenneth D. Merry.
+ * 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.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * 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.
+ *
+ *	$Id$
+ */
+
+#include <sys/types.h>
+#include <sys/sysctl.h>
+#include <sys/errno.h>
+#include <sys/dkstat.h>
+
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "devstat.h"
+
+char devstat_errbuf[DEVSTAT_ERRBUF_SIZE];
+
+/*
+ * Table to match descriptive strings with device types.  These are in
+ * order from most common to least common to speed search time.
+ */
+struct devstat_match_table match_table[] = {
+	{"da",		DEVSTAT_TYPE_DIRECT,	DEVSTAT_MATCH_TYPE},
+	{"cd",		DEVSTAT_TYPE_CDROM,	DEVSTAT_MATCH_TYPE},
+	{"scsi",	DEVSTAT_TYPE_IF_SCSI,	DEVSTAT_MATCH_IF},
+	{"ide",		DEVSTAT_TYPE_IF_IDE,	DEVSTAT_MATCH_IF},
+	{"other",	DEVSTAT_TYPE_IF_OTHER,	DEVSTAT_MATCH_IF},
+	{"worm",	DEVSTAT_TYPE_WORM,	DEVSTAT_MATCH_TYPE},
+	{"sa",		DEVSTAT_TYPE_SEQUENTIAL,DEVSTAT_MATCH_TYPE},
+	{"pass",	DEVSTAT_TYPE_PASS,	DEVSTAT_MATCH_PASS},
+	{"optical",	DEVSTAT_TYPE_OPTICAL,	DEVSTAT_MATCH_TYPE},
+	{"array",	DEVSTAT_TYPE_STORARRAY,	DEVSTAT_MATCH_TYPE},
+	{"changer",	DEVSTAT_TYPE_CHANGER,	DEVSTAT_MATCH_TYPE},
+	{"scanner",	DEVSTAT_TYPE_SCANNER,	DEVSTAT_MATCH_TYPE},
+	{"printer",	DEVSTAT_TYPE_PRINTER,	DEVSTAT_MATCH_TYPE},
+	{"floppy",	DEVSTAT_TYPE_FLOPPY,	DEVSTAT_MATCH_TYPE},
+	{"proc",	DEVSTAT_TYPE_PROCESSOR,	DEVSTAT_MATCH_TYPE},
+	{"comm",	DEVSTAT_TYPE_COMM,	DEVSTAT_MATCH_TYPE},
+	{"enclosure",	DEVSTAT_TYPE_ENCLOSURE,	DEVSTAT_MATCH_TYPE},
+	{NULL,		0,			0}
+};
+
+/*
+ * Local function declarations.
+ */
+static int compare_select(const void *arg1, const void *arg2);
+
+int
+getnumdevs(void)
+{
+	size_t numdevsize;
+	int numdevs;
+	char *func_name = "getnumdevs";
+
+	numdevsize = sizeof(int);
+
+	/*
+	 * Find out how many devices we have in the system.
+	 */
+	if (sysctlbyname("kern.devstat.numdevs", &numdevs,
+			 &numdevsize, NULL, 0) == -1) {
+		sprintf(devstat_errbuf, "%s: error getting number of devices\n"
+			"%s: %s", func_name, func_name, strerror(errno));
+		return(-1);
+	} else
+		return(numdevs);
+}
+
+/*
+ * This is an easy way to get the generation number, but the generation is
+ * supplied in a more atmoic manner by the kern.devstat.all sysctl.
+ * Because this generation sysctl is separate from the statistics sysctl,
+ * the device list and the generation could change between the time that
+ * this function is called and the device list is retreived.
+ */
+int
+getgeneration(void)
+{
+	size_t gensize;
+	int generation;
+	char *func_name = "getgeneration";
+
+	gensize = sizeof(int);
+
+	/*
+	 * Get the current generation number.
+	 */
+	if (sysctlbyname("kern.devstat.generation", &generation, 
+			 &gensize, NULL, 0) == -1) {
+		sprintf(devstat_errbuf,"%s: error getting devstat generation\n"
+			"%s: %s", func_name, func_name, strerror(errno));
+		return(-1);
+	} else
+		return(generation);
+}
+
+/*
+ * Get the current devstat version.  The return value of this function
+ * should be compared with DEVSTAT_VERSION, which is defined in
+ * sys/devicestat.h.  This will enable userland programs to determine
+ * whether they are out of sync with the kernel.
+ */
+int
+getversion(void)
+{
+	size_t versize;
+	int version;
+	char *func_name = "getversion";
+
+	versize = sizeof(int);
+
+	/*
+	 * Get the current devstat version.
+	 */
+	if (sysctlbyname("kern.devstat.version", &version, &versize,
+			 NULL, 0) == -1) {
+		sprintf(devstat_errbuf, "%s: error getting devstat version\n"
+			"%s: %s", func_name, func_name, strerror(errno));
+		return(-1);
+	} else
+		return(version);
+}
+
+/*
+ * Check the devstat version we know about against the devstat version the
+ * kernel knows about.  If they don't match, print an error into the
+ * devstat error buffer, and return -1.  If they match, return 0.
+ */
+int
+checkversion(void)
+{
+	int retval = 0;
+	int errlen = 0;
+	char *func_name = "checkversion";
+
+	if (getversion() != DEVSTAT_VERSION) {
+		char tmpstr[256];
+
+		errlen = snprintf(devstat_errbuf, DEVSTAT_ERRBUF_SIZE,
+				  "%s: userland devstat version %d is not "
+				  "the same as the kernel\n%s: devstat "
+				  "version %d\n", func_name, DEVSTAT_VERSION,
+				  func_name, getversion());
+
+                if (getversion() < DEVSTAT_VERSION)
+			snprintf(tmpstr, sizeof(tmpstr),
+				 "%s: you really should know better"
+				 " than to upgrade your\n%s: "
+				 "userland binaries without "
+				 "upgrading your kernel\n",
+				 func_name, func_name);
+                else
+			snprintf(tmpstr, sizeof(tmpstr),
+				 "%s: you really should know better"
+				 " than to upgrade your kernel "
+				 "without\n%s: upgrading your "
+				 "userland binaries\n",
+				 func_name, func_name);
+
+		strncat(devstat_errbuf, tmpstr,
+			DEVSTAT_ERRBUF_SIZE - errlen - 1);
+
+		retval = -1;
+	}
+
+	return(retval);
+}
+
+/*
+ * Get the current list of devices and statistics, and the current
+ * generation number.
+ * 
+ * Return values:
+ * -1  -- error
+ *  0  -- device list is unchanged
+ *  1  -- device list has changed
+ */
+int
+getdevs(struct statinfo *stats)
+{
+	int error;
+	size_t dssize;
+	int oldnumdevs, oldgeneration;
+	int retval = 0;
+	struct devinfo *dinfo;
+	char *func_name = "getdevs";
+
+	dinfo = stats->dinfo;
+
+	if (dinfo == NULL) {
+		sprintf(devstat_errbuf, "%s: stats->dinfo was NULL", func_name);
+		return(-1);
+	}
+
+	oldnumdevs = dinfo->numdevs;
+	oldgeneration = dinfo->generation;
+
+	/*
+	 * If this is our first time through, mem_ptr will be null.  
+	 */
+	if (dinfo->mem_ptr == NULL) {
+		/*
+		 * Get the number of devices.  If it's negative, it's an
+		 * error.  Don't bother setting the error string, since
+		 * getnumdevs() has already done that for us.
+		 */
+		if ((dinfo->numdevs = getnumdevs()) < 0)
+			return(-1);
+
+		/*
+		 * The kern.devstat.all sysctl returns the current generation
+		 * number, as well as all the devices.  So we need four
+		 * bytes more.
+		 */
+		dssize =(dinfo->numdevs * sizeof(struct devstat)) + sizeof(int);
+		dinfo->mem_ptr = (u_int8_t *)malloc(dssize);
+	} else
+		dssize =(dinfo->numdevs * sizeof(struct devstat)) + sizeof(int);
+
+	/* Get the current time when we get the stats */
+	gettimeofday(&stats->busy_time, NULL);
+
+	/*
+	 * Request all of the devices.  We only really allow for one
+	 * ENOMEM failure.  It would, of course, be possible to just go in
+	 * a loop and keep reallocing the device structure until we don't
+	 * get ENOMEM back.  I'm not sure it's worth it, though.  If
+	 * devices are being added to the system that quickly, maybe the
+	 * user can just wait until all devices are added.
+	 */
+	if ((error = sysctlbyname("kern.devstat.all", dinfo->mem_ptr, 
+	     &dssize, NULL, 0)) == -1) {
+		/*
+		 * If we get ENOMEM back, that means that there are 
+		 * more devices now, so we need to allocate more 
+		 * space for the device array.
+		 */
+		if (errno == ENOMEM) {
+			/*
+			 * No need to set the error string here, getnumdevs()
+			 * will do that if it fails.
+			 */
+			if ((dinfo->numdevs = getnumdevs()) < 0)
+				return(-1);
+
+			dssize = (dinfo->numdevs * sizeof(struct devstat)) +
+				sizeof(int);
+			dinfo->mem_ptr = (u_int8_t *)realloc(dinfo->mem_ptr,
+							     dssize);
+			if ((error = sysctlbyname("kern.devstat.all", 
+			    dinfo->mem_ptr, &dssize, NULL, 0)) == -1) {
+				sprintf(devstat_errbuf,
+					"%s: error getting device stats\n"
+					"%s: %s", func_name, func_name,
+					strerror(errno));
+				return(-1);
+			}
+		} else {
+			sprintf(devstat_errbuf,
+				"%s: error getting device stats\n"
+				"%s: %s", func_name, func_name,
+				strerror(errno));
+			return(-1);
+		}
+	} 
+
+	/*
+	 * The sysctl spits out the generation as the first four bytes,
+	 * then all of the device statistics structures.
+	 */
+	dinfo->generation = *(int *)dinfo->mem_ptr;
+
+	/*
+	 * If the generation has changed, and if the current number of
+	 * devices is not the same as the number of devices recorded in the
+	 * devinfo structure, it is likely that the device list has shrunk.
+	 * The reason that it is likely that the device list has shrunk in
+	 * this case is that if the device list has grown, the sysctl above
+	 * will return an ENOMEM error, and we will reset the number of
+	 * devices and reallocate the device array.  If the second sysctl
+	 * fails, we will return an error and therefore never get to this
+	 * point.  If the device list has shrunk, the sysctl will not
+	 * return an error since we have more space allocated than is
+	 * necessary.  So, in the shrinkage case, we catch it here and
+	 * reallocate the array so that we don't use any more space than is
+	 * necessary.
+	 */
+	if (oldgeneration != dinfo->generation) {
+		if (getnumdevs() != dinfo->numdevs) {
+			if ((dinfo->numdevs = getnumdevs()) < 0)
+				return(-1);
+			dssize = (dinfo->numdevs * sizeof(struct devstat)) +
+				sizeof(int);
+			dinfo->mem_ptr = (u_int8_t *)realloc(dinfo->mem_ptr,
+							     dssize);
+		}
+		retval = 1;
+	}
+
+	dinfo->devices = (struct devstat *)(dinfo->mem_ptr + sizeof(int));
+
+	return(retval);
+}
+
+/*
+ * selectdevs():
+ *
+ * Devices are selected/deselected based upon the following criteria:
+ * - devices specified by the user on the command line
+ * - devices matching any device type expressions given on the command line
+ * - devices with the highest I/O, if 'top' mode is enabled
+ * - the first n unselected devices in the device list, if maxshowdevs
+ *   devices haven't already been selected and if the user has not
+ *   specified any devices on the command line and if we're in "add" mode.
+ *
+ * Input parameters:
+ * - device selection list (dev_select)
+ * - current number of devices selected (num_selected)
+ * - total number of devices in the selection list (num_selections)
+ * - devstat generation as of the last time selectdevs() was called
+ *   (select_generation)
+ * - current devstat generation (current_generation)
+ * - current list of devices and statistics (devices)
+ * - number of devices in the current device list (numdevs)
+ * - compiled version of the command line device type arguments (matches)
+ *   - This is optional.  If the number of devices is 0, this will be ignored.
+ *   - The matching code pays attention to the current selection mode.  So
+ *     if you pass in a matching expression, it will be evaluated based
+ *     upon the selection mode that is passed in.  See below for details.
+ * - number of device type matching expressions (num_matches)
+ *   - Set to 0 to disable the matching code.
+ * - list of devices specified on the command line by the user (dev_selections)
+ * - number of devices selected on the command line by the user
+ *   (num_dev_selections)
+ * - Our selection mode.  There are four different selection modes:
+ *      - add mode.  (DS_SELECT_ADD) Any devices matching devices explicitly
+ *        selected by the user or devices matching a pattern given by the
+ *        user will be selected in addition to devices that are already
+ *        selected.  Additional devices will be selected, up to maxshowdevs
+ *        number of devices. 
+ *      - only mode. (DS_SELECT_ONLY)  Only devices matching devices
+ *        explicitly given by the user or devices matching a pattern
+ *        given by the user will be selected.  No other devices will be
+ *        selected.
+ *      - addonly mode.  (DS_SELECT_ADDONLY)  This is similar to add and
+ *        only.  Basically, this will not de-select any devices that are
+ *        current selected, as only mode would, but it will also not
+ *        gratuitously select up to maxshowdevs devices as add mode would.
+ *      - remove mode.  (DS_SELECT_REMOVE)  Any devices matching devices
+ *        explicitly selected by the user or devices matching a pattern
+ *        given by the user will be de-selected.
+ * - maximum number of devices we can select (maxshowdevs)
+ * - flag indicating whether or not we're in 'top' mode (perf_select)
+ *
+ * Output data:
+ * - the device selection list may be modified and passed back out
+ * - the number of devices selected and the total number of items in the
+ *   device selection list may be changed
+ * - the selection generation may be changed to match the current generation
+ * 
+ * Return values:
+ * -1  -- error
+ *  0  -- selected devices are unchanged
+ *  1  -- selected devices changed
+ */
+int
+selectdevs(struct device_selection **dev_select, int *num_selected,
+	   int *num_selections, int *select_generation, 
+	   int current_generation, struct devstat *devices, int numdevs,
+	   struct devstat_match *matches, int num_matches,
+	   char **dev_selections, int num_dev_selections,
+	   devstat_select_mode select_mode, int maxshowdevs, int perf_select)
+{
+	register int i, j, k;
+	int init_selections = 0, init_selected_var = 0;
+	struct device_selection *old_dev_select = NULL;
+	int old_num_selections = 0, old_num_selected;
+	int selection_number = 0;
+	int changed = 0, found = 0;
+
+	if ((dev_select == NULL) || (devices == NULL) || (numdevs <= 0))
+		return(-1);
+
+	/*
+	 * We always want to make sure that we have as many dev_select
+	 * entries as there are devices. 
+	 */
+	/*
+	 * In this case, we haven't selected devices before.
+	 */
+	if (*dev_select == NULL) {
+		*dev_select = (struct device_selection *)malloc(numdevs *
+			sizeof(struct device_selection));
+		*select_generation = current_generation;
+		init_selections = 1;
+		changed = 1;
+	/*
+	 * In this case, we have selected devices before, but the device
+	 * list has changed since we last selected devices, so we need to
+	 * either enlarge or reduce the size of the device selection list.
+	 */
+	} else if (*num_selections != numdevs) {
+		*dev_select = (struct device_selection *)realloc(*dev_select,
+			numdevs * sizeof(struct device_selection));
+		*select_generation = current_generation;
+		init_selections = 1;
+	/*
+	 * In this case, we've selected devices before, and the selection
+	 * list is the same size as it was the last time, but the device
+	 * list has changed.
+	 */
+	} else if (*select_generation < current_generation) {
+		*select_generation = current_generation;
+		init_selections = 1;
+	}
+
+	/*
+	 * If we're in "only" mode, we want to clear out the selected
+	 * variable since we're going to select exactly what the user wants
+	 * this time through.
+	 */
+	if (select_mode == DS_SELECT_ONLY)
+		init_selected_var = 1;
+
+	/*
+	 * In all cases, we want to back up the number of selected devices.
+	 * It is a quick and accurate way to determine whether the selected
+	 * devices have changed.
+	 */
+	old_num_selected = *num_selected;
+
+	/*
+	 * We want to make a backup of the current selection list if 
+	 * the list of devices has changed, or if we're in performance 
+	 * selection mode.  In both cases, we don't want to make a backup
+	 * if we already know for sure that the list will be different.
+	 * This is certainly the case if this is our first time through the
+	 * selection code.
+	 */
+	if (((init_selected_var != 0) || (init_selections != 0)
+	 || (perf_select != 0)) && (changed == 0)){
+		old_dev_select = (struct device_selection *)malloc(
+		    *num_selections * sizeof(struct device_selection));
+		old_num_selections = *num_selections;
+		bcopy(*dev_select, old_dev_select, 
+		    sizeof(struct device_selection) * *num_selections);
+	}
+
+	if (init_selections != 0) {
+		bzero(*dev_select, sizeof(struct device_selection) * numdevs);
+
+		for (i = 0; i < numdevs; i++) {
+			(*dev_select)[i].device_number = 
+				devices[i].device_number;
+			strncpy((*dev_select)[i].device_name,
+				devices[i].device_name,
+				DEVSTAT_NAME_LEN);
+			(*dev_select)[i].unit_number = devices[i].unit_number;
+			(*dev_select)[i].position = i;
+		}
+		*num_selections = numdevs;
+	} else if (init_selected_var != 0) {
+		for (i = 0; i < numdevs; i++) 
+			(*dev_select)[i].selected = 0;
+	}
+
+	/* we haven't gotten around to selecting anything yet.. */
+	if ((select_mode == DS_SELECT_ONLY) || (init_selections != 0)
+	 || (init_selected_var != 0))
+		*num_selected = 0;
+
+	/*
+	 * Look through any devices the user specified on the command line
+	 * and see if they match known devices.  If so, select them.
+	 */
+	for (i = 0; (i < *num_selections) && (num_dev_selections > 0); i++) {
+		char tmpstr[80];
+
+		sprintf(tmpstr, "%s%d", (*dev_select)[i].device_name,
+			(*dev_select)[i].unit_number);
+		for (j = 0; j < num_dev_selections; j++) {
+			if (strcmp(tmpstr, dev_selections[j]) == 0) {
+				/*
+				 * Here we do different things based on the
+				 * mode we're in.  If we're in add or
+				 * addonly mode, we only select this device
+				 * if it hasn't already been selected.
+				 * Otherwise, we would be unnecessarily
+				 * changing the selection order and
+				 * incrementing the selection count.  If
+				 * we're in only mode, we unconditionally
+				 * select this device, since in only mode
+				 * any previous selections are erased and
+				 * manually specified devices are the first
+				 * ones to be selected.  If we're in remove
+				 * mode, we de-select the specified device and
+				 * decrement the selection count.
+				 */
+				switch(select_mode) {
+				case DS_SELECT_ADD:
+				case DS_SELECT_ADDONLY:
+					if ((*dev_select)[i].selected)
+						break;
+					/* FALLTHROUGH */
+				case DS_SELECT_ONLY:
+					(*dev_select)[i].selected =
+						++selection_number;
+					(*num_selected)++;
+					break;
+				case DS_SELECT_REMOVE:
+					(*dev_select)[i].selected = 0;
+					(*num_selected)--;
+					/*
+					 * This isn't passed back out, we
+					 * just use it to keep track of
+					 * how many devices we've removed.
+					 */
+					num_dev_selections--;
+					break;
+				}
+				break;
+			}
+		}
+	}
+
+	/*
+	 * Go through the user's device type expressions and select devices
+	 * accordingly.  We only do this if the number of devices already
+	 * selected is less than the maximum number we can show.
+	 */
+	for (i = 0; (i < num_matches) && (*num_selected < maxshowdevs); i++) {
+		/* We should probably indicate some error here */
+		if ((matches[i].match_fields == DEVSTAT_MATCH_NONE)
+		 || (matches[i].num_match_categories <= 0))
+			continue;
+
+		for (j = 0; j < numdevs; j++) {
+			int num_match_categories;
+
+			num_match_categories = matches[i].num_match_categories;
+
+			/*
+			 * Determine whether or not the current device
+			 * matches the given matching expression.  This if
+			 * statement consists of three components:
+			 *   - the device type check
+			 *   - the device interface check
+			 *   - the passthrough check
+			 * If a the matching test is successful, it 
+			 * decrements the number of matching categories,
+			 * and if we've reached the last element that
+			 * needed to be matched, the if statement succeeds.
+			 * 
+			 */
+			if ((((matches[i].match_fields & DEVSTAT_MATCH_TYPE)!=0)
+			  && ((devices[j].device_type & DEVSTAT_TYPE_MASK) ==
+			        (matches[i].device_type & DEVSTAT_TYPE_MASK))
+			  &&(((matches[i].match_fields & DEVSTAT_MATCH_PASS)!=0)
+			   || (((matches[i].match_fields & 
+				DEVSTAT_MATCH_PASS) == 0)
+			    && ((devices[j].device_type &
+			        DEVSTAT_TYPE_PASS) == 0)))
+			  && (--num_match_categories == 0)) 
+			 || (((matches[i].match_fields & DEVSTAT_MATCH_IF) != 0)
+			  && ((devices[j].device_type & DEVSTAT_TYPE_IF_MASK) ==
+			        (matches[i].device_type & DEVSTAT_TYPE_IF_MASK))
+			  &&(((matches[i].match_fields & DEVSTAT_MATCH_PASS)!=0)
+			   || (((matches[i].match_fields &
+				DEVSTAT_MATCH_PASS) == 0)
+			    && ((devices[j].device_type & 
+				DEVSTAT_TYPE_PASS) == 0)))
+			  && (--num_match_categories == 0))
+			 || (((matches[i].match_fields & DEVSTAT_MATCH_PASS)!=0)
+			  && ((devices[j].device_type & DEVSTAT_TYPE_PASS) != 0)
+			  && (--num_match_categories == 0))) {
+
+				/*
+				 * This is probably a non-optimal solution
+				 * to the problem that the devices in the
+				 * device list will not be in the same
+				 * order as the devices in the selection
+				 * array.
+				 */
+				for (k = 0; k < numdevs; k++) {
+					if ((*dev_select)[k].position == j) {
+						found = 1;
+						break;
+					}
+				}
+
+				/*
+				 * There shouldn't be a case where a device
+				 * in the device list is not in the
+				 * selection list...but it could happen.
+				 */
+				if (found != 1) {
+					fprintf(stderr, "selectdevs: couldn't"
+						" find %s%d in selection "
+						"list\n",
+						devices[j].device_name,
+						devices[j].unit_number);
+					break;
+				}
+
+				/*
+				 * We do different things based upon the
+				 * mode we're in.  If we're in add or only
+				 * mode, we go ahead and select this device
+				 * if it hasn't already been selected.  If
+				 * it has already been selected, we leave
+				 * it alone so we don't mess up the
+				 * selection ordering.  Manually specified
+				 * devices have already been selected, and
+				 * they have higher priority than pattern
+				 * matched devices.  If we're in remove
+				 * mode, we de-select the given device and
+				 * decrement the selected count.
+				 */
+				switch(select_mode) {
+				case DS_SELECT_ADD:
+				case DS_SELECT_ADDONLY:
+				case DS_SELECT_ONLY:
+					if ((*dev_select)[k].selected != 0)
+						break;
+					(*dev_select)[k].selected =
+						++selection_number;
+					(*num_selected)++;
+					break;
+				case DS_SELECT_REMOVE:
+					(*dev_select)[k].selected = 0;
+					(*num_selected)--;
+					break;
+				}
+			}
+		}
+	}
+
+	/*
+	 * Here we implement "top" mode.  Devices are sorted in the
+	 * selection array based on two criteria:  whether or not they are
+	 * selected (not selection number, just the fact that they are
+	 * selected!) and the number of bytes in the "bytes" field of the
+	 * selection structure.  The bytes field generally must be kept up
+	 * by the user.  In the future, it may be maintained by library
+	 * functions, but for now the user has to do the work.
+	 *
+	 * At first glance, it may seem wrong that we don't go through and
+	 * select every device in the case where the user hasn't specified
+	 * any devices or patterns.  In fact, though, it won't make any
+	 * difference in the device sorting.  In that particular case (i.e.
+	 * when we're in "add" or "only" mode, and the user hasn't
+	 * specified anything) the first time through no devices will be
+	 * selected, so the only criterion used to sort them will be their
+	 * performance.  The second time through, and every time thereafter,
+	 * all devices will be selected, so again selection won't matter.
+	 */
+	if (perf_select != 0) {
+
+		/* Sort the device array by throughput  */
+		qsort(*dev_select, *num_selections,
+		      sizeof(struct device_selection),
+		      compare_select);
+
+		if (*num_selected == 0) {
+			/*
+			 * Here we select every device in the array, if it
+			 * isn't already selected.  Because the 'selected'
+			 * variable in the selection array entries contains
+			 * the selection order, the devstats routine can show
+			 * the devices that were selected first.
+			 */
+			for (i = 0; i < *num_selections; i++) {
+				if ((*dev_select)[i].selected == 0) {
+					(*dev_select)[i].selected =
+						++selection_number;
+					(*num_selected)++;
+				}
+			}
+		} else {
+			selection_number = 0;
+			for (i = 0; i < *num_selections; i++) {
+				if ((*dev_select)[i].selected != 0) {
+					(*dev_select)[i].selected =
+						++selection_number;
+				}
+			}
+		}
+	}
+
+	/*
+	 * If we're in the "add" selection mode and if we haven't already
+	 * selected maxshowdevs number of devices, go through the array and
+	 * select any unselected devices.  If we're in "only" mode, we
+	 * obviously don't want to select anything other than what the user
+	 * specifies.  If we're in "remove" mode, it probably isn't a good
+	 * idea to go through and select any more devices, since we might
+	 * end up selecting something that the user wants removed.  Through
+	 * more complicated logic, we could actually figure this out, but
+	 * that would probably require combining this loop with the various
+	 * selections loops above.
+	 */
+	if ((select_mode == DS_SELECT_ADD) && (*num_selected < maxshowdevs)) {
+		for (i = 0; i < *num_selections; i++)
+			if ((*dev_select)[i].selected == 0) {
+				(*dev_select)[i].selected = ++selection_number;
+				(*num_selected)++;
+			}
+	}
+
+	/*
+	 * Look at the number of devices that have been selected.  If it
+	 * has changed, set the changed variable.  Otherwise, if we've
+	 * made a backup of the selection list, compare it to the current
+	 * selection list to see if the selected devices have changed.
+	 */
+	if ((changed == 0) && (old_num_selected != *num_selected))
+		changed = 1;
+	else if ((changed == 0) && (old_dev_select != NULL)) {
+		/*
+		 * Now we go through the selection list and we look at
+		 * it three different ways.
+		 */
+		for (i = 0; (i < *num_selections) && (changed == 0) && 
+		     (i < old_num_selections); i++) {
+			/*
+			 * If the device at index i in both the new and old
+			 * selection arrays has the same device number and
+			 * selection status, it hasn't changed.  We
+			 * continue on to the next index.
+			 */
+			if (((*dev_select)[i].device_number ==
+			     old_dev_select[i].device_number)
+			 && ((*dev_select)[i].selected == 
+			     old_dev_select[i].selected))
+				continue;
+
+			/*
+			 * Now, if we're still going through the if
+			 * statement, the above test wasn't true.  So we
+			 * check here to see if the device at index i in
+			 * the current array is the same as the device at
+			 * index i in the old array.  If it is, that means
+			 * that its selection number has changed.  Set
+			 * changed to 1 and exit the loop.
+			 */
+			else if ((*dev_select)[i].device_number ==
+			          old_dev_select[i].device_number) {
+				changed = 1;
+				break;
+			}
+			/*
+			 * If we get here, then the device at index i in
+			 * the current array isn't the same device as the
+			 * device at index i in the old array.
+			 */
+			else {
+				int found = 0;
+
+				/*
+				 * Search through the old selection array
+				 * looking for a device with the same
+				 * device number as the device at index i
+				 * in the current array.  If the selection
+				 * status is the same, then we mark it as
+				 * found.  If the selection status isn't
+				 * the same, we break out of the loop.
+				 * Since found isn't set, changed will be
+				 * set to 1 below.
+				 */
+				for (j = 0; j < old_num_selections; j++) {
+					if (((*dev_select)[i].device_number ==
+					      old_dev_select[j].device_number)
+					 && ((*dev_select)[i].selected ==
+					      old_dev_select[j].selected)){
+						found = 1;
+						break;
+					}
+					else if ((*dev_select)[i].device_number
+					    == old_dev_select[j].device_number)
+						break;
+				}
+				if (found == 0)
+					changed = 1;
+			}
+		}
+	}
+	if (old_dev_select != NULL)
+		free(old_dev_select);
+
+	return(changed);
+}
+
+/*
+ * Comparison routine for qsort() above.  Note that the comparison here is
+ * backwards -- generally, it should return a value to indicate whether
+ * arg1 is <, =, or > arg2.  Instead, it returns the opposite.  The reason
+ * it returns the opposite is so that the selection array will be sorted in
+ * order of decreasing performance.  We sort on two parameters.  The first
+ * sort key is whether or not one or the other of the devices in question
+ * has been selected.  If one of them has, and the other one has not, the
+ * selected device is automatically more important than the unselected
+ * device.  If neither device is selected, we judge the devices based upon
+ * performance.
+ */
+static int
+compare_select(const void *arg1, const void *arg2)
+{
+	if ((((struct device_selection *)arg1)->selected)
+	 && (((struct device_selection *)arg2)->selected == 0))
+		return(-1);
+	else if ((((struct device_selection *)arg1)->selected == 0)
+	      && (((struct device_selection *)arg2)->selected))
+		return(1);
+	else if (((struct device_selection *)arg2)->bytes <
+	         ((struct device_selection *)arg1)->bytes)
+		return(-1);
+	else if (((struct device_selection *)arg2)->bytes >
+		 ((struct device_selection *)arg1)->bytes)
+		return(1);
+	else
+		return(0);
+}
+
+/*
+ * Take a string with the general format "arg1,arg2,arg3", and build a
+ * device matching expression from it.
+ */
+int
+buildmatch(char *match_str, struct devstat_match **matches, int *num_matches)
+{
+	char *tstr[5];
+	char **tempstr;
+	int num_args;
+	register int i, j;
+	char *func_name = "buildmatch";
+
+	/* We can't do much without a string to parse */
+	if (match_str == NULL) {
+		sprintf(devstat_errbuf, "%s: no match expression", func_name);
+		return(-1);
+	}
+
+	/*
+	 * Break the (comma delimited) input string out into separate strings.
+	 */
+	for (tempstr = tstr, num_args  = 0; 
+	     (*tempstr = strsep(&match_str, ",")) != NULL && (num_args < 5); 
+	     num_args++)
+		if (**tempstr != '\0')
+			if (++tempstr >= &tstr[5])
+				break;
+
+	/* The user gave us too many type arguments */
+	if (num_args > 3) {
+		sprintf(devstat_errbuf, "%s: too many type arguments",
+			func_name);
+		return(-1);
+	}
+
+	/*
+	 * Since you can't realloc a pointer that hasn't been malloced
+	 * first, we malloc first and then realloc.
+	 */
+	if (*num_matches == 0)
+		*matches = (struct devstat_match *)malloc(
+			   sizeof(struct devstat_match));
+	else
+		*matches = (struct devstat_match *)realloc(*matches,
+			  sizeof(struct devstat_match) * (*num_matches + 1));
+			  
+	/* Make sure the current entry is clear */
+	bzero(&matches[0][*num_matches], sizeof(struct devstat_match));
+
+	/*
+	 * Step through the arguments the user gave us and build a device
+	 * matching expression from them.
+	 */
+	for (i = 0; i < num_args; i++) {
+		char *tempstr2, *tempstr3;
+
+		/*
+		 * Get rid of leading white space.
+		 */
+		tempstr2 = tstr[i];
+		while (isspace(*tempstr2) && (*tempstr2 != '\0'))
+			tempstr2++;
+
+		/*
+		 * Get rid of trailing white space.
+		 */
+		tempstr3 = &tempstr2[strlen(tempstr2) - 1];
+
+		while ((*tempstr3 != '\0') && (tempstr3 > tempstr2)
+		    && (isspace(*tempstr3))) {
+			*tempstr3 = '\0';
+			tempstr3--;
+		}
+
+		/*
+		 * Go through the match table comparing the user's
+		 * arguments to known device types, interfaces, etc.  
+		 */
+		for (j = 0; match_table[j].match_str != NULL; j++) {
+			/*
+			 * We do case-insensitive matching, in case someone
+			 * wants to enter "SCSI" instead of "scsi" or
+			 * something like that.  Only compare as many 
+			 * characters as are in the string in the match 
+			 * table.  This should help if someone tries to use 
+			 * a super-long match expression.  
+			 */
+			if (strncasecmp(tempstr2, match_table[j].match_str,
+			    strlen(match_table[j].match_str)) == 0) {
+				/*
+				 * Make sure the user hasn't specified two
+				 * items of the same type, like "da" and
+				 * "cd".  One device cannot be both.
+				 */
+				if (((*matches)[*num_matches].match_fields &
+				    match_table[j].match_field) != 0) {
+					sprintf(devstat_errbuf,
+						"%s: cannot have more than "
+						"one match item in a single "
+						"category", func_name);
+					return(-1);
+				}
+				/*
+				 * If we've gotten this far, we have a
+				 * winner.  Set the appropriate fields in
+				 * the match entry.
+				 */
+				(*matches)[*num_matches].match_fields |=
+					match_table[j].match_field;
+				(*matches)[*num_matches].device_type |=
+					match_table[j].type;
+				(*matches)[*num_matches].num_match_categories++;
+				break;
+			}
+		}
+		/*
+		 * We should have found a match in the above for loop.  If
+		 * not, that means the user entered an invalid device type
+		 * or interface.
+		 */
+		if ((*matches)[*num_matches].num_match_categories != (i + 1)) {
+			sprintf(devstat_errbuf,
+				"%s: unknown match item \"%s\"", func_name,
+				tstr[i]);
+			return(-1);
+		}
+	}
+
+	(*num_matches)++;
+
+	return(0);
+}
+
+/*
+ * Compute a number of device statistics.  Only one field is mandatory, and
+ * that is "current".  Everything else is optional.  The caller passes in
+ * pointers to variables to hold the various statistics he desires.  If he
+ * doesn't want a particular staistic, he should pass in a NULL pointer.
+ * Return values:
+ * 0   -- success
+ * -1  -- failure
+ */
+int
+compute_stats(struct devstat *current, struct devstat *previous,
+	      long double etime, u_int64_t *total_bytes,
+	      u_int64_t *total_transfers, u_int64_t *total_blocks,
+	      long double *kb_per_transfer, long double *transfers_per_second,
+	      long double *mb_per_second, long double *blocks_per_second,
+	      long double *ms_per_transaction)
+{
+	u_int64_t totalbytes, totaltransfers, totalblocks;
+	char *func_name = "compute_stats";
+
+	/*
+	 * current is the only mandatory field.
+	 */
+	if (current == NULL) {
+		sprintf(devstat_errbuf, "%s: current stats structure was NULL",
+			func_name);
+		return(-1);
+	}
+
+	totalbytes = (current->bytes_written + current->bytes_read) -
+		     ((previous) ? (previous->bytes_written +
+				    previous->bytes_read) : 0);
+
+	if (total_bytes)
+		*total_bytes = totalbytes;
+
+	totaltransfers = (current->num_reads +
+			  current->num_writes +
+			  current->num_other) -
+			 ((previous) ?
+			  (previous->num_reads +
+			   previous->num_writes +
+			   previous->num_other) : 0);
+	if (total_transfers)
+		*total_transfers = totaltransfers;
+
+	if (transfers_per_second) {
+		if (etime > 0.0) {
+			*transfers_per_second = totaltransfers;
+			*transfers_per_second /= etime;
+		} else
+			*transfers_per_second = 0.0;
+	}
+
+	if (kb_per_transfer) {
+		*kb_per_transfer = totalbytes;
+		*kb_per_transfer /= 1024;
+		if (totaltransfers > 0)
+			*kb_per_transfer /= totaltransfers;
+		else
+			*kb_per_transfer = 0.0;
+	}
+
+	if (mb_per_second) {
+		*mb_per_second = totalbytes;
+		*mb_per_second /= 1024 * 1024;
+		if (etime > 0.0)
+			*mb_per_second /= etime;
+		else
+			*mb_per_second = 0.0;
+	}
+
+	totalblocks = totalbytes;
+	if (current->block_size > 0)
+		totalblocks /= current->block_size;
+	else
+		totalblocks /= 512;
+
+	if (total_blocks)
+		*total_blocks = totalblocks;
+
+	if (blocks_per_second) {
+		*blocks_per_second = totalblocks;
+		if (etime > 0.0)
+			*blocks_per_second /= etime;
+		else
+			*blocks_per_second = 0.0;
+	}
+
+	if (ms_per_transaction) {
+		if (totaltransfers > 0) {
+			*ms_per_transaction = etime;
+			*ms_per_transaction /= totaltransfers;
+			*ms_per_transaction *= 1000;
+		} else
+			*ms_per_transaction = 0.0;
+	}
+
+	return(0);
+}
+
+long double
+compute_etime(struct timeval cur_time, struct timeval prev_time)
+{
+	struct timeval busy_time;
+	u_int64_t busy_usec;
+	long double etime;
+
+	timersub(&cur_time, &prev_time, &busy_time);
+
+        busy_usec = busy_time.tv_sec;  
+        busy_usec *= 1000000;          
+        busy_usec += busy_time.tv_usec;
+        etime = busy_usec;
+        etime /= 1000000;
+
+	return(etime);
+}
diff --git a/lib/libdevstat/devstat.h b/lib/libdevstat/devstat.h
new file mode 100644
index 0000000..b2f1543
--- /dev/null
+++ b/lib/libdevstat/devstat.h
@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 1997, 1998 Kenneth D. Merry.
+ * 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.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * 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.
+ *
+ *	$Id$
+ */
+
+#ifndef _DEVSTAT_H
+#define _DEVSTAT_H
+#include <sys/cdefs.h>
+#include <sys/devicestat.h>
+
+#define DEVSTAT_ERRBUF_SIZE  2048 /* size of the devstat library error string */
+
+extern char devstat_errbuf[];
+
+typedef enum {
+	DEVSTAT_MATCH_NONE	= 0x00,
+	DEVSTAT_MATCH_TYPE	= 0x01,
+	DEVSTAT_MATCH_IF	= 0x02,
+	DEVSTAT_MATCH_PASS	= 0x04
+} devstat_match_flags;
+
+struct devstat_match {
+	devstat_match_flags	match_fields;
+	devstat_type_flags	device_type;
+	int			num_match_categories;
+};
+
+struct devstat_match_table {
+	char 			*match_str;
+	devstat_type_flags	type;
+	devstat_match_flags	match_field;
+};
+
+struct device_selection {
+	u_int32_t	device_number;
+	char		device_name[DEVSTAT_NAME_LEN];
+	int		unit_number;
+	int		selected;
+	u_int64_t	bytes;
+	int		position;
+};
+
+struct devinfo {
+	struct devstat	*devices;
+	u_int8_t	*mem_ptr;
+	int		generation;
+	int		numdevs;
+};
+
+struct statinfo {
+	long		cp_time[CPUSTATES];
+	long		tk_nin;
+	long		tk_nout;
+	struct devinfo	*dinfo;
+	struct timeval	busy_time;
+};
+
+typedef enum {
+	DS_SELECT_ADD,
+	DS_SELECT_ONLY,
+	DS_SELECT_REMOVE,
+	DS_SELECT_ADDONLY
+} devstat_select_mode;
+
+__BEGIN_DECLS
+int getnumdevs(void);
+int getgeneration(void);
+int getversion(void);
+int checkversion(void);
+int getdevs(struct statinfo *stats);
+int selectdevs(struct device_selection **dev_select, int *num_selected,
+	       int *num_selections, int *select_generation, 
+	       int current_generation, struct devstat *devices, int numdevs,
+	       struct devstat_match *matches, int num_matches,
+	       char **dev_selections, int num_dev_selections,
+	       devstat_select_mode select_mode, int maxshowdevs,
+	       int perf_select);
+int buildmatch(char *match_str, struct devstat_match **matches,
+	       int *num_matches);
+int compute_stats(struct devstat *current, struct devstat *previous,
+		  long double etime, u_int64_t *total_bytes,
+		  u_int64_t *total_transfers, u_int64_t *total_blocks,
+		  long double *kb_per_transfer,
+		  long double *transfers_per_second, long double *mb_per_second,
+		  long double *blocks_per_second,
+		  long double *ms_per_transaction);
+long double compute_etime(struct timeval cur_time, struct timeval prev_time);
+__END_DECLS
+
+#endif /* _DEVSTAT_H  */