956 lines
24 KiB
Groff
956 lines
24 KiB
Groff
.\"
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.\" Copyright (c) 1998, 1999, 2001 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 July 15, 2001
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.Dt DEVSTAT 3
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.Os
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.Sh NAME
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.Nm devstat ,
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.Nm devstat_getnumdevs ,
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.Nm devstat_getgeneration ,
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.Nm devstat_getversion ,
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.Nm devstat_checkversion ,
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.Nm devstat_getdevs ,
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.Nm devstat_selectdevs ,
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.Nm devstat_buildmatch ,
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.Nm devstat_compute_statistics ,
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.Nm devstat_compute_etime ,
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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 LIBRARY
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.Lb libdevstat
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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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.Fo devstat_getnumdevs
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.Fa "kvm_t *kd"
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.Fc
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.Ft long
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.Fo devstat_getgeneration
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.Fa "kvm_t *kd"
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.Fc
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.Ft int
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.Fo devstat_getversion
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.Fa "kvm_t *kd"
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.Fc
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.Ft int
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.Fo devstat_checkversion
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.Fa "kvm_t *kd"
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.Fc
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.Ft int
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.Fo devstat_getdevs
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.Fa "kvm_t *kd"
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.Fa "struct statinfo *stats"
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.Fc
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.Ft int
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.Fo devstat_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 devstat_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 devstat_compute_statistics
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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 "..."
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.Fc
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.Ft long double
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.Fo devstat_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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.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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and
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.Xr kvm 3 .
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All functions that take a
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.Vt kvm_t *
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as first argument can be passed
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.Dv NULL
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instead of a kvm handle as this argument,
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which causes the data to be read via
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.Xr sysctl 3 .
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Otherwise, it is read via
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.Xr kvm 3
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using the supplied handle.
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.Fn devstat_checkversion
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should be called with each kvm handle that is going to be used (or with
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.Dv NULL
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if
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.Xr sysctl 3
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is going to be used).
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.Pp
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.Fn devstat_getnumdevs
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returns the number of devices registered with the
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.Nm
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subsystem in the kernel.
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.Pp
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.Fn getnumdevs
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is a deprecated version of
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.Fn devstat_getnumdevs
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which always uses
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.Xr sysctl 3 .
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.Pp
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.Fn devstat_getgeneration
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returns the current generation of the
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.Nm
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list of devices in the kernel.
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.Pp
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.Fn getgeneration
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is a deprecated version of
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.Fn devstat_getgeneration
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which always uses
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.Xr sysctl 3 .
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.Pp
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.Fn devstat_getversion
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returns the current kernel
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.Nm
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version.
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.Pp
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.Fn getversion
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is a deprecated version of
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.Fn devstat_getversion
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which always uses
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.Xr sysctl 3 .
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.Pp
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.Fn devstat_checkversion
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checks the userland devstat version against the kernel devstat version.
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If the two are identical, it returns zero.
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Otherwise, it prints an 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 checkversion
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is a deprecated version of
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.Fn devstat_checkversion
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which always uses
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.Xr sysctl 3 .
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.Pp
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.Fn devstat_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.
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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 devstat_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 and zeroed prior to the first invocation of
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.Fn devstat_getdevs .
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The
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.Va dinfo
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subelement is used to store state between calls, and should not be modified
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after the first call to
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.Fn devstat_getdevs .
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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
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structures, but at the head of the array is the current
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.Nm
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generation.
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The reason the generation is at the head of the buffer is so that userland
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software accessing the devstat statistics information can atomically get
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both the statistics information and the corresponding generation number.
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If client software were forced to get the generation 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 devstat_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 (or the corresponding values read via
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.Xr kvm 3 ) .
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The generation subelement of the
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.Va devinfo
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structure contains the corresponding generation number.
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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
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subsystem.
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.Pp
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.Fn getdevs
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is a deprecated version of
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.Fn devstat_getdevs
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which always uses
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.Xr sysctl 3 .
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.Pp
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.Fn devstat_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.
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These are generally 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 devstat_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 devstat_selectdevs .
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The
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.Va bytes
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value currently must be maintained by the user.
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In the future, 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.
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If devices have been selected by name or pattern, the performance tracking
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code will honor those selections and will only sort among the selected
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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 devstat_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 devstat_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 devstat_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 devstat_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 devstat_selectdevs
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will remove devices specified by name or by matching pattern.
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It will not 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 devstat_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.
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It will not, however, select 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 devstat_selectdevs
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will not select any more than
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.Va maxshowdevs
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devices.
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One exception to this is when you are in
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.Dq top
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mode and no devices have been selected.
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In this case,
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.Fn devstat_selectdevs
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will select every device in the system.
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Client programs must pay attention to selection order when deciding whether
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to pay attention to a particular device.
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This may be the wrong behavior, and probably requires additional thought.
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.Pp
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.Fn devstat_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 devstat_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.
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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 devstat_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 selectdevs
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is the old name of
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.Fn devstat_selectdevs ,
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and is deprecated.
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.Pp
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.Fn devstat_buildmatch
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take a comma separated match string and compile 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 devstat_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 9n -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 9n -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 9n -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 buildmatch
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is the old name of
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.Fn devstat_buildmatch ,
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and is deprecated.
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.Pp
|
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.Fn devstat_compute_statistics
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|
is an updated version of
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.Fn compute_stats
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that provides more complete statistics calculation.
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There are four arguments for which values \fBmust\fR be supplied:
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.Va current ,
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.Va previous ,
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.Va etime ,
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and the terminating argument for the varargs list,
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.Va DSM_NONE .
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For most applications, the user will want to supply valid devstat
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structures for both
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.Va current
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and
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.Va previous .
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In some instances, for instance when calculating statistics since system
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boot, the user may pass in a NULL pointer for the
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.Va previous
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argument.
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In that case,
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.Fn devstat_compute_statistics
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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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For each statistic to be calculated, the user should supply the proper
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enumerated type (listed below), and a variable of the indicated type.
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All statistics are either integer values, for which a u_int64_t is used,
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or floating point, for which a long double is used.
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The statistics that may be calculated are:
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.Bl -tag -width DSM_TRANSFERS_PER_SECOND_OTHER
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.It DSM_NONE
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type: N/A
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.Pp
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This \fBmust\fR
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be the last argument passed to
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.Fn devstat_compute_statistics .
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It is an argument list terminator.
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.It DSM_TOTAL_BYTES
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type: u_int64_t *
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.Pp
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The total number of bytes transferred between the acquisition of
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.Va previous
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and
|
|
.Va current .
|
|
.It DSM_TOTAL_BYTES_READ
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of bytes read between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TOTAL_BYTES_WRITE
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of bytes written between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TOTAL_TRANSFERS
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of transfers between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TOTAL_TRANSFERS_READ
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of reads between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TOTAL_TRANSFERS_WRITE
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of writes between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TOTAL_TRANSFERS_OTHER
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of transactions that are not reads or writes that occurred
|
|
between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TOTAL_BLOCKS
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of blocks transferred between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
This number is in terms of the blocksize reported by the device.
|
|
If no blocksize has been reported (i.e. the block size is 0), a default
|
|
blocksize of 512 bytes will be used in the calculation.
|
|
.It DSM_TOTAL_BLOCKS_READ
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of blocks read between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
This number is in terms of the blocksize reported by the device.
|
|
If no blocksize has been reported (i.e. the block size is 0), a default
|
|
blocksize of 512 bytes will be used in the calculation.
|
|
.It DSM_TOTAL_BLOCKS_WRITE
|
|
type: u_int64_t *
|
|
.Pp
|
|
The total number of blocks written between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
This number is in terms of the blocksize reported by the device.
|
|
If no blocksize has been reported (i.e. the block size is 0), a default
|
|
blocksize of 512 bytes will be used in the calculation.
|
|
.It DSM_KB_PER_TRANSFER
|
|
type: long double *
|
|
.Pp
|
|
The average number of kilobytes per transfer between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_KB_PER_TRANSFER_READ
|
|
type: long double *
|
|
.Pp
|
|
The average number of kilobytes per read transaction between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_KB_PER_TRANSFER_WRITE
|
|
type: long double *
|
|
.Pp
|
|
The average number of kilobytes per write transaction between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TRANSFERS_PER_SECOND
|
|
type: long double *
|
|
.Pp
|
|
The average number of transfers per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TRANSFERS_PER_SECOND_READ
|
|
type: long double *
|
|
.Pp
|
|
The average number of reads per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TRANSFERS_PER_SECOND_WRITE
|
|
type: long double *
|
|
.Pp
|
|
The average number of writes per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_TRANSFERS_PER_SECOND_OTHER
|
|
type: long double *
|
|
.Pp
|
|
The average number of non-read, non-write transactions per second between
|
|
the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_MB_PER_SECOND
|
|
type: long double *
|
|
.Pp
|
|
The average number of megabytes transferred per second between the
|
|
acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_MB_PER_SECOND_READ
|
|
type: long double *
|
|
.Pp
|
|
The average number of megabytes read per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_MB_PER_SECOND_WRITE
|
|
type: long double *
|
|
.Pp
|
|
The average number of megabytes written per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
.It DSM_BLOCKS_PER_SECOND
|
|
type: long double *
|
|
.Pp
|
|
The average number of blocks transferred per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
This number is in terms of the blocksize reported by the device.
|
|
If no blocksize has been reported (i.e. the block size is 0), a default
|
|
blocksize of 512 bytes will be used in the calculation.
|
|
.It DSM_BLOCKS_PER_SECOND_READ
|
|
type: long double *
|
|
.Pp
|
|
The average number of blocks read per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
This number is in terms of the blocksize reported by the device.
|
|
If no blocksize has been reported (i.e. the block size is 0), a default
|
|
blocksize of 512 bytes will be used in the calculation.
|
|
.It DSM_BLOCKS_PER_SECOND_WRITE
|
|
type: long double *
|
|
.Pp
|
|
The average number of blocks written per second between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
This number is in terms of the blocksize reported by the device.
|
|
If no blocksize has been reported (i.e. the block size is 0), a default
|
|
blocksize of 512 bytes will be used in the calculation.
|
|
.It DSM_MS_PER_TRANSACTION
|
|
type: long double *
|
|
.Pp
|
|
The average rate of transaction completion between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
Note that this isn't a true reflection of the average number of
|
|
milliseconds per transaction, but rather is the average rate of transaction
|
|
completion.
|
|
The number is derived by dividing the time elapsed by the number of
|
|
transactions completed.
|
|
.It DSM_MS_PER_TRANSACTION_READ
|
|
type: long double *
|
|
.Pp
|
|
The average rate of read completions between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
As above, this is not the true number of milliseconds per transaction, but
|
|
rather the average rate of read transaction completion.
|
|
.It DSM_MS_PER_TRANSACTION_WRITE
|
|
type: long double *
|
|
.Pp
|
|
The average rate of write transaction completion between the acquisition of
|
|
.Va previous
|
|
and
|
|
.Va current .
|
|
As above, this is not the true number of milliseconds per transaction, but
|
|
rather the average rate of write transaction completion.
|
|
.It DSM_SKIP
|
|
type: N/A
|
|
.Pp
|
|
If you do not need a result from
|
|
.Fn devstat_compute_statistics ,
|
|
just put
|
|
.Va DSM_SKIP
|
|
as first (type) parameter and
|
|
.Va NULL
|
|
as second parameter.
|
|
This can be useful in scenarios where the statistics to be calculated
|
|
are determined at run time.
|
|
.El
|
|
.Pp
|
|
.Fn compute_stats
|
|
is deprecated; use
|
|
.Fn devstat_compute_statistics
|
|
instead.
|
|
.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 milliseconds per transaction.
|
|
.El
|
|
.Pp
|
|
.Fn devstat_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 devstat_getdevs
|
|
function (in struct
|
|
.Va statinfo )
|
|
each time it fetches the current
|
|
.Nm
|
|
list.
|
|
.Pp
|
|
.Fn compute_etime
|
|
is the old name of
|
|
.Fn devstat_compute_etime ,
|
|
and is deprecated.
|
|
.Sh RETURN VALUES
|
|
.Fn devstat_getnumdevs ,
|
|
.Fn devstat_getgeneration ,
|
|
and
|
|
.Fn devstat_getversion
|
|
return the indicated \fBsysctl\fR variable, or -1 if there is an error
|
|
fetching the variable.
|
|
.Pp
|
|
.Fn devstat_checkversion
|
|
returns 0 if the kernel and userland
|
|
.Nm
|
|
versions match.
|
|
If they do not match, it returns -1.
|
|
.Pp
|
|
.Fn devstat_getdevs
|
|
and
|
|
.Fn devstat_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 devstat_getdevs
|
|
is usually a hint to re-run
|
|
.Fn devstat_selectdevs
|
|
because the device list has changed.
|
|
.Pp
|
|
.Fn devstat_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 devstat_compute_etime
|
|
returns the computed elapsed time.
|
|
.Pp
|
|
.Fn devstat_compute_statistics
|
|
returns -1 for error, and 0 for success.
|
|
.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 kvm 3 ,
|
|
.Xr sysctl 3 ,
|
|
.Xr iostat 8 ,
|
|
.Xr rpc.rstatd 8 ,
|
|
.Xr sysctl 8 ,
|
|
.Xr vmstat 8 ,
|
|
.Xr devstat 9
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
statistics system first appeared in
|
|
.Fx 3.0 .
|
|
The new interface (the functions prefixed with devstat_) first appeared in
|
|
.Fx 5.0 .
|
|
.Sh AUTHORS
|
|
.An Kenneth Merry Aq ken@FreeBSD.org
|
|
.Sh BUGS
|
|
There should probably be an interface to de-allocate memory allocated by
|
|
.Fn devstat_getdevs ,
|
|
.Fn devstat_selectdevs ,
|
|
and
|
|
.Fn devstat_buildmatch .
|
|
.Pp
|
|
.Fn devstat_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.
|