535 lines
14 KiB
Groff
535 lines
14 KiB
Groff
.\"
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.\" Copyright (c) 1998 Kenneth D. Merry.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd May 21, 1998
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.Dt DEVSTAT 3
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.Os FreeBSD 3.0
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.Sh NAME
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.Nm devstat ,
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.Nm getnumdevs ,
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.Nm getgeneration ,
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.Nm getversion ,
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.Nm checkversion ,
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.Nm getdevs ,
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.Nm selectdevs ,
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.Nm buildmatch ,
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.Nm compute_stats ,
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.Nm compute_etime
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.Nd device statistics utility library
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.Sh SYNOPSIS
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.Fd #include <sys/dkstat.h>
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.Fd #include <devstat.h>
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.Ft int
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.Fn getnumdevs "void"
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.Ft long
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.Fn getgeneration "void"
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.Ft int
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.Fn getversion "void"
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.Ft int
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.Fn checkversion "void"
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.Ft int
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.Fn getdevs "struct statinfo *stats"
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.Ft int
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.Fo selectdevs
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.Fa "struct device_selection **dev_select"
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.Fa "int *num_selected"
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.Fa "int *num_selections"
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.Fa "long *select_generation"
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.Fa "long current_generation"
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.Fa "struct devstat *devices"
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.Fa "int numdevs"
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.Fa "struct devstat_match *matches"
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.Fa "int num_matches"
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.Fa "char **dev_selections"
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.Fa "int num_dev_selections"
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.Fa "devstat_select_mode select_mode"
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.Fa "int maxshowdevs"
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.Fa "int perf_select"
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.Fc
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.Ft int
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.Fo buildmatch
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.Fa "char *match_str"
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.Fa "struct devstat_match **matches"
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.Fa "int *num_matches"
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.Fc
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.Ft int
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.Fo compute_stats
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.Fa "struct devstat *current"
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.Fa "struct devstat *previous"
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.Fa "long double etime"
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.Fa "u_int64_t *total_bytes"
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.Fa "u_int64_t *total_transfers"
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.Fa "u_int64_t *total_blocks"
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.Fa "long double *kb_per_transfer"
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.Fa "long double *transfers_per_second"
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.Fa "long double *mb_per_second"
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.Fa "long double *blocks_per_second"
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.Fa "long double *ms_per_transaction"
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.Fc
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.Ft long double
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.Fo compute_etime
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.Fa "struct timeval cur_time"
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.Fa "struct timeval prev_time"
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.Fc
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.Sh DESCRIPTION
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The
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.Nm
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library is a library of helper functions for dealing with the kernel
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.Xr devstat 9
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interface, which is accessible to users via
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.Xr sysctl 3 .
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.Pp
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.Fn getnumdevs
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returns the number of devices registered with the
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.Nm devstat
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subsystem in the kernel.
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.Pp
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.Fn getgeneration
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returns the current generation of the
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.Nm devstat
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list of devices in the kernel.
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.Pp
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.Fn getversion
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returns the current kernel
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.Nm devstat
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version.
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.Pp
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.Fn checkversion
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checks the userland devstat version against the kernel devstat version. If
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the two are identical, it returns zero. Otherwise, it prints an
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appropriate error in
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.Va devstat_errbuf
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and returns -1.
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.Pp
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.Fn getdevs
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fetches the current list of devices and statistics into the supplied
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.Va statinfo
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structure. The
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.Va statinfo
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structure can be found in
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.Aq Pa devstat.h :
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.Bd -literal -offset indent
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struct statinfo {
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long cp_time[CPUSTATES];
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long tk_nin;
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long tk_nout;
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struct devinfo *dinfo;
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struct timeval busy_time;
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};
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.Ed
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.Pp
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.Fn getdevs
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expects the
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.Va statinfo
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structure to be allocated, and it also expects the
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.Va dinfo
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subelement to be allocated ahead of time. The
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.Va dinfo
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subelement contains the following elements:
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.Bd -literal -offset indent
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struct devinfo {
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struct devstat *devices;
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u_int8_t *mem_ptr;
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long generation;
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int numdevs;
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};
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.Ed
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.Pp
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The
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.Va kern.devstat.all
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.Nm sysctl
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variable contains an array of
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.Nm devstat
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structures, but at the head of the array is the current
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.Nm devstat
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generation. The reason the generation is at the head of the buffer is so
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that userland software accessing the devstat statistics information can
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atomically get both the statistics information and the corresponding
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generation number. If client software were forced to get the generation
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number via a separate
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.Nm sysctl
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variable (which is available for convenience), the list of devices could
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change between the time the client gets the generation and the time the
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client gets the device list.
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.Pp
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The
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.Va mem_ptr
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subelement of the
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.Va devinfo
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structure is a pointer to memory that is allocated, and resized if
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necessary, by
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.Fn getdevs .
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The devices subelement of the
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.Va devinfo
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structure is basically a pointer to the beginning of the array of devstat
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structures from the
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.Va kern.devstat.all
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.Nm sysctl
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variable. The generation subelement of the
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.Nm devinfo
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structure contains the generation number from the
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.Va kern.devstat.all
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.Nm sysctl
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variable.
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The
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.Va numdevs
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subelement of the
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.Va devinfo
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structure contains the current
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number of devices registered with the kernel
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.Nm devstat
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subsystem.
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.Pp
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.Fn selectdevs
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selects devices to display based upon a number of criteria:
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.Bl -tag -width flag
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.It specified devices
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Specified devices are the first selection priority. These are generally
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devices specified by name by the user. e.g. da0, da1, cd0.
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.It match patterns
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These are pattern matching expressions generated by
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.Fn buildmatch
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from user input.
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.It performance
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If performance mode is enabled, devices will be sorted based on the
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.Va bytes
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field in the
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.Va device_selection
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structure passed in to
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.Fn selectdevs .
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The
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.Va bytes
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value currently must be maintained by the user. In the future,
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this may be done for him in a
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.Nm
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library routine.
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If no devices have been selected by name or by pattern, the performance
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tracking code will select every device in the system, and sort them by
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performance. If devices have been selected by name or pattern, the
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performance tracking code will honor those selections and will only sort
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among the selected devices.
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.It order in the devstat list
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If the selection mode is set to DS_SELECT_ADD, and if there are still less
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than
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.Va maxshowdevs
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devices selected,
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.Fn selectdevs
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will automatically select up to
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.Va maxshowdevs
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devices.
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.El
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.Pp
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.Fn selectdevs
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performs selections in four different modes:
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.Bl -tag -width DS_SELECT_ADDONLY
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.It DS_SELECT_ADD
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In add mode,
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.Fn selectdevs
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will select any unselected devices specified by name or matching pattern.
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It will also select more devices, in devstat list order, until the number
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of selected devices is equal to
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.Va maxshowdevs
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or until all devices are
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selected.
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.It DS_SELECT_ONLY
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In only mode,
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.Fn selectdevs
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will clear all current selections, and will only select devices specified
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by name or by matching pattern.
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.It DS_SELECT_REMOVE
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In remove mode,
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.Fn selectdevs
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will remove devices specified by name or by matching pattern. It will not
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select any additional devices.
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.It DS_SELECT_ADDONLY
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In add only mode,
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.Fn selectdevs
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will select any unselected devices specified by name or matching pattern.
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In this respect it is identical to add mode. It will not, however, select
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any devices other than those specified.
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.El
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.Pp
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In all selection modes,
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.Fn selectdevs
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will not select any more than
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.Va maxshowdevs
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devices. One exception to
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this is when you are in
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.Dq top
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mode and no devices have been selected. In
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this case,
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.Fn selectdevs
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will select every device in the system. Client programs must pay attention
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to selection order when deciding whether to pay attention to a particular
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device. This may be the wrong behavior, and probably requires additional
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thought.
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.Pp
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.Fn selectdevs
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handles allocation and resizing of the
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.Va dev_select
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structure passed in
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by the client.
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.Fn selectdevs
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uses the
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.Va numdevs
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and
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.Va current_generation
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fields to track the
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current
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.Nm
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generation and number of devices. If
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.Va num_selections
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is not the same
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as
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.Va numdevs
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or if
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.Va select_generation
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is not the same as
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.Va current_generation ,
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.Fn selectdevs
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will resize the selection list as necessary, and re-initialize the
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selection array.
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.Pp
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.Fn buildmatch
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takes a comma separated match string and compiles it into a
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\fBdevstat_match\fR structure that is understood by
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.Fn selectdevs .
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Match strings have the following format:
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.Pp
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.Bd -literal -offset indent
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device,type,if
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.Ed
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.Pp
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.Fn buildmatch
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takes care of allocating and reallocating the match list as necessary.
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Currently known match types include:
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.Pp
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.Bl -tag -width indent -compact
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.It device type:
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.Bl -tag -width 123456789 -compact
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.It da
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Direct Access devices
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.It sa
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Sequential Access devices
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.It printer
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Printers
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.It proc
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Processor devices
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.It worm
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Write Once Read Multiple devices
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.It cd
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CD devices
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.It scanner
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Scanner devices
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.It optical
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Optical Memory devices
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.It changer
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Medium Changer devices
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.It comm
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Communication devices
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.It array
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Storage Array devices
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.It enclosure
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Enclosure Services devices
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.It floppy
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Floppy devices
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.El
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.Pp
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.It interface:
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.Bl -tag -width 123456789 -compact
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.It IDE
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Integrated Drive Electronics devices
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.It SCSI
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Small Computer System Interface devices
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.It other
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Any other device interface
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.El
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.Pp
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.It passthrough:
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.Bl -tag -width 123456789 -compact
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.It pass
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Passthrough devices
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.El
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.El
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.Pp
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.Fn compute_stats
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provides an easy way to obtain various device statistics. Only two
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arguments are mandatory:
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.Va current
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and
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.Va etime .
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Every other argument is optional. For most applications, the user will
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want to supply both
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.Va current
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and
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.Va previous
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devstat structures so that statistics may be calculated over a given period
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of time. In some instances, for instance when calculating statistics since
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system boot, the user may pass in a NULL pointer for the
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.Va previous
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argument. In that case,
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.Fn compute_stats
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will use the total stats in the
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.Va current
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structure to calculate statistics over
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.Va etime .
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The various statistics that may be calculated by
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.Fn compute_stats
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should be mostly explained by the function declaration itself, but for
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completeness here is a list of variable names and the statistics that will
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be put in them:
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.Bl -tag -width transfers_per_second
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.It total_bytes
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This is the total number of bytes transferred on the given device, both
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reads and writes, between the acquisition of
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.Va previous
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and the acquisition of
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.Va current .
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If
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.Va previous
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is NULL, the result will be the total reads and writes given in
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.Va current .
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.It total_transfers
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This is the total number of transfers completed between the
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acquisition of
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.Va previous
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and the acquisition of
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.Va current .
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If
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.Va previous
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is NULL, the result will be the total number of transactions listed in
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.Va current .
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.It total_blocks
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This is basically
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.Va total_bytes
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divided by the device blocksize. If the device blocksize is listed as
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.Sq 0 ,
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the device blocksize will default to 512 bytes.
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.It kb_per_transfer
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This is the average number of kilobytes per transfer during the measurement
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period.
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.It transfers_per_second
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This is the average number of transfers per second.
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.It mb_per_second
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This is average megabytes per second.
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.It blocks_per_second
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This is average blocks per second. If the device blocksize is
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.Sq 0 ,
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a default blocksize of 512 bytes will be used instead.
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.It ms_per_transaction
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The average number of milliseconds per transaction.
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.El
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.Pp
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.Fn compute_etime
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provides an easy way to find the difference in seconds between two
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.Va timeval
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structures. This is most commonly used in conjunction with the time
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recorded by the
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.Fn getdevs
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function (in struct
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.Va statinfo )
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each time it fetches the current
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.Nm
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list.
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.Sh RETURN VALUES
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.Fn getnumdevs ,
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.Fn getgeneration ,
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and
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.Fn getversion
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return the indicated \fBsysctl\fR variable, or -1 if there is an error
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fetching the variable.
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.Pp
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.Fn checkversion
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returns 0 if the kernel and userland
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.Nm devstat
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versions match. If they do not match, it returns -1.
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.Pp
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.Fn getdevs
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and
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.Fn selectdevs
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return -1 in case of an error, 0 if there is no error and 1 if the device
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list or selected devices have changed. A return value of 1 from
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.Fn getdevs
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is usually a hint to re-run
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.Fn selectdevs
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because the device list has changed.
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.Pp
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.Fn buildmatch
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returns -1 for error, and 0 if there is no error.
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.Pp
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.Fn compute_stats
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returns -1 for error, and 0 for success.
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.Pp
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.Fn compute_etime
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returns the computed elapsed time.
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.Pp
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If an error is returned from one of the
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.Nm
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library functions, the reason for the error is generally printed in
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the global string
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.Va devstat_errbuf
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which is
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.Dv DEVSTAT_ERRBUF_SIZE
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characters long.
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.Sh SEE ALSO
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.Xr systat 1 ,
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.Xr iostat 8 ,
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.Xr rpc.rstatd 8 ,
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.Xr vmstat 8 ,
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.Xr devstat 9
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.Sh HISTORY
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The
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.Nm
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statistics system first appeared in
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.Fx 3.0 .
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.Sh AUTHORS
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.An Kenneth Merry Aq ken@FreeBSD.ORG
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.Sh BUGS
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There should probably be an interface to de-allocate memory allocated by
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.Fn getdevs ,
|
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.Fn selectdevs ,
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and
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.Fn buildmatch .
|
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.Pp
|
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.Fn selectdevs
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should probably not select more than
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.Va maxshowdevs
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devices in
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.Dq top
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mode when no devices have been selected previously.
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.Pp
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There should probably be functions to perform the statistics buffer
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swapping that goes on in most of the clients of this library.
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.Pp
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The
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.Va statinfo
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and
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.Va devinfo
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structures should probably be cleaned up and thought out a little more.
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