summaryrefslogtreecommitdiffstats
path: root/lib/libdevstat/devstat.3
blob: df2b9dc144f5989c0b67357b1a211a2d99f58e17 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
.\"
.\" Copyright (c) 1998, 1999 Kenneth D. Merry.
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd May 21, 1998
.Dt DEVSTAT 3
.Os FreeBSD 3.0
.Sh NAME
.Nm devstat ,
.Nm getnumdevs ,
.Nm getgeneration ,
.Nm getversion ,
.Nm checkversion ,
.Nm getdevs ,
.Nm selectdevs ,
.Nm buildmatch ,
.Nm compute_stats ,
.Nm compute_etime
.Nd device statistics utility library
.Sh LIBRARY
.Lb libdevstat
.Sh SYNOPSIS
.Fd #include <sys/dkstat.h>
.Fd #include <devstat.h>
.Ft int
.Fn getnumdevs "void"
.Ft long
.Fn getgeneration "void"
.Ft int
.Fn getversion "void"
.Ft int
.Fn checkversion "void"
.Ft int
.Fn getdevs "struct statinfo *stats"
.Ft int
.Fo selectdevs
.Fa "struct device_selection **dev_select"
.Fa "int *num_selected"
.Fa "int *num_selections"
.Fa "long *select_generation"
.Fa "long current_generation"
.Fa "struct devstat *devices"
.Fa "int numdevs"
.Fa "struct devstat_match *matches"
.Fa "int num_matches"
.Fa "char **dev_selections"
.Fa "int num_dev_selections"
.Fa "devstat_select_mode select_mode"
.Fa "int maxshowdevs"
.Fa "int perf_select"
.Fc
.Ft int
.Fo buildmatch
.Fa "char *match_str"
.Fa "struct devstat_match **matches"
.Fa "int *num_matches"
.Fc
.Ft int
.Fo compute_stats
.Fa "struct devstat *current"
.Fa "struct devstat *previous"
.Fa "long double etime"
.Fa "u_int64_t *total_bytes"
.Fa "u_int64_t *total_transfers"
.Fa "u_int64_t *total_blocks"
.Fa "long double *kb_per_transfer"
.Fa "long double *transfers_per_second"
.Fa "long double *mb_per_second"
.Fa "long double *blocks_per_second"
.Fa "long double *ms_per_transaction"
.Fc
.Ft long double
.Fo compute_etime
.Fa "struct timeval cur_time"
.Fa "struct timeval prev_time"
.Fc
.Sh DESCRIPTION
The
.Nm
library is a library of helper functions for dealing with the kernel
.Xr devstat 9
interface, which is accessible to users via
.Xr sysctl 3 .
.Pp
.Fn getnumdevs
returns the number of devices registered with the
.Nm devstat
subsystem in the kernel.
.Pp
.Fn getgeneration
returns the current generation of the
.Nm devstat
list of devices in the kernel.
.Pp
.Fn getversion
returns the current kernel
.Nm devstat
version.
.Pp
.Fn checkversion
checks the userland devstat version against the kernel devstat version.  If
the two are identical, it returns zero.  Otherwise, it prints an
appropriate error in 
.Va devstat_errbuf
and returns -1.
.Pp
.Fn getdevs
fetches the current list of devices and statistics into the supplied
.Va statinfo
structure.  The
.Va statinfo
structure can be found in 
.Aq Pa devstat.h :
.Bd -literal -offset indent
struct statinfo {
	long            cp_time[CPUSTATES];
	long            tk_nin;  
	long            tk_nout;
	struct devinfo  *dinfo;
	struct timeval  busy_time;
};
.Ed
.Pp
.Fn getdevs
expects the
.Va statinfo
structure to be allocated, and it also expects the
.Va dinfo
subelement to be allocated and zeroed prior to the first invocation of
.Fn getdevs .
The
.Va dinfo
subelement is used to store state between calls, and should not be modified
after the first call to
.Fn getdevs .
The
.Va dinfo
subelement contains the following elements:
.Bd -literal -offset indent
struct devinfo {
	struct devstat	*devices;
	u_int8_t	*mem_ptr;
	long		generation;
	int		numdevs;
};
.Ed
.Pp
The
.Va kern.devstat.all
.Nm sysctl
variable contains an array of
.Nm devstat
structures, but at the head of the array is the current
.Nm devstat
generation.  The reason the generation is at the head of the buffer is so
that userland software accessing the devstat statistics information can
atomically get both the statistics information and the corresponding
generation number.  If client software were forced to get the generation
number via a separate
.Nm sysctl
variable (which is available for convenience), the list of devices could
change between the time the client gets the generation and the time the
client gets the device list.
.Pp
The
.Va mem_ptr
subelement of the
.Va devinfo
structure is a pointer to memory that is allocated, and resized if
necessary, by
.Fn getdevs .
The devices subelement of the
.Va devinfo
structure is basically a pointer to the beginning of the array of devstat
structures from the
.Va kern.devstat.all
.Nm sysctl
variable.  The generation subelement of the
.Nm devinfo
structure contains the generation number from the
.Va kern.devstat.all
.Nm sysctl
variable.  
The
.Va numdevs
subelement of the 
.Va devinfo
structure contains the current
number of devices registered with the kernel
.Nm devstat
subsystem.
.Pp
.Fn selectdevs
selects devices to display based upon a number of criteria:
.Bl -tag -width flag
.It specified devices
Specified devices are the first selection priority.  These are generally
devices specified by name by the user.  e.g. da0, da1, cd0.
.It match patterns
These are pattern matching expressions generated by
.Fn buildmatch
from user input.
.It performance
If performance mode is enabled, devices will be sorted based on the
.Va bytes
field in the 
.Va device_selection
structure passed in to
.Fn selectdevs .
The 
.Va bytes
value currently must be maintained by the user.  In the future,
this may be done for him in a
.Nm
library routine.
If no devices have been selected by name or by pattern, the performance
tracking code will select every device in the system, and sort them by
performance.  If devices have been selected by name or pattern, the
performance tracking code will honor those selections and will only sort
among the selected devices.
.It order in the devstat list
If the selection mode is set to DS_SELECT_ADD, and if there are still less
than 
.Va maxshowdevs
devices selected,
.Fn selectdevs
will automatically select up to 
.Va maxshowdevs
devices.
.El
.Pp
.Fn selectdevs
performs selections in four different modes:
.Bl -tag -width DS_SELECT_ADDONLY
.It DS_SELECT_ADD
In add mode,
.Fn selectdevs
will select any unselected devices specified by name or matching pattern.
It will also select more devices, in devstat list order, until the number
of selected devices is equal to 
.Va maxshowdevs
or until all devices are
selected.
.It DS_SELECT_ONLY
In only mode,
.Fn selectdevs
will clear all current selections, and will only select devices specified
by name or by matching pattern.
.It DS_SELECT_REMOVE
In remove mode,
.Fn selectdevs
will remove devices specified by name or by matching pattern.  It will not
select any additional devices.
.It DS_SELECT_ADDONLY
In add only mode,
.Fn selectdevs
will select any unselected devices specified by name or matching pattern.
In this respect it is identical to add mode.  It will not, however, select
any devices other than those specified.
.El
.Pp
In all selection modes,
.Fn selectdevs
will not select any more than 
.Va maxshowdevs
devices.  One exception to
this is when you are in
.Dq top
mode and no devices have been selected.  In
this case,
.Fn selectdevs
will select every device in the system.  Client programs must pay attention
to selection order when deciding whether to pay attention to a particular
device.  This may be the wrong behavior, and probably requires additional
thought.
.Pp
.Fn selectdevs
handles allocation and resizing of the 
.Va dev_select
structure passed in
by the client.
.Fn selectdevs
uses the 
.Va numdevs
and 
.Va current_generation
fields to track the
current
.Nm
generation and number of devices.  If 
.Va num_selections
is not the same
as 
.Va numdevs
or if 
.Va select_generation
is not the same as 
.Va current_generation ,
.Fn selectdevs
will resize the selection list as necessary, and re-initialize the
selection array.
.Pp
.Fn buildmatch
takes a comma separated match string and compiles it into a
\fBdevstat_match\fR structure that is understood by
.Fn selectdevs .
Match strings have the following format:
.Pp
.Bd -literal -offset indent
device,type,if
.Ed
.Pp
.Fn buildmatch
takes care of allocating and reallocating the match list as necessary.
Currently known match types include:
.Pp
.Bl -tag -width indent -compact
.It device type:
.Bl -tag -width 123456789 -compact
.It da 
Direct Access devices
.It sa
Sequential Access devices
.It printer
Printers
.It proc
Processor devices
.It worm
Write Once Read Multiple devices
.It cd
CD devices
.It scanner
Scanner devices
.It optical
Optical Memory devices
.It changer
Medium Changer devices
.It comm
Communication devices
.It array
Storage Array devices
.It enclosure
Enclosure Services devices
.It floppy
Floppy devices
.El
.Pp
.It interface:
.Bl -tag -width 123456789 -compact
.It IDE
Integrated Drive Electronics devices
.It SCSI
Small Computer System Interface devices
.It other
Any other device interface
.El
.Pp
.It passthrough:
.Bl -tag -width 123456789 -compact
.It pass
Passthrough devices
.El
.El
.Pp
.Fn compute_stats
provides an easy way to obtain various device statistics.  Only two
arguments are mandatory:
.Va current
and
.Va etime .
Every other argument is optional.  For most applications, the user will
want to supply both
.Va current
and
.Va previous
devstat structures so that statistics may be calculated over a given period
of time.  In some instances, for instance when calculating statistics since
system boot, the user may pass in a NULL pointer for the
.Va previous
argument.  In that case,
.Fn compute_stats
will use the total stats in the
.Va current
structure to calculate statistics over
.Va etime .
The various statistics that may be calculated by
.Fn compute_stats
should be mostly explained by the function declaration itself, but for
completeness here is a list of variable names and the statistics that will
be put in them:
.Bl -tag -width transfers_per_second
.It total_bytes
This is the total number of bytes transferred on the given device, both
reads and writes, between the acquisition of
.Va previous
and the acquisition of
.Va current .
If
.Va previous
is NULL, the result will be the total reads and writes given in
.Va current .
.It total_transfers
This is the total number of transfers completed between the
acquisition of
.Va previous
and the acquisition of
.Va current .
If
.Va previous
is NULL, the result will be the total number of transactions listed in
.Va current .
.It total_blocks
This is basically
.Va total_bytes
divided by the device blocksize.  If the device blocksize is listed as 
.Sq 0 ,
the device blocksize will default to 512 bytes.
.It kb_per_transfer
This is the average number of kilobytes per transfer during the measurement
period.
.It transfers_per_second
This is the average number of transfers per second.
.It mb_per_second
This is average megabytes per second.
.It blocks_per_second
This is average blocks per second.  If the device blocksize is
.Sq 0 ,
a default blocksize of 512 bytes will be used instead.
.It ms_per_transaction
The average number of milliseconds per transaction.
.El
.Pp
.Fn compute_etime
provides an easy way to find the difference in seconds between two
.Va timeval
structures.  This is most commonly used in conjunction with the time
recorded by the
.Fn getdevs
function (in struct 
.Va statinfo )
each time it fetches the current
.Nm
list.
.Sh RETURN VALUES
.Fn getnumdevs ,
.Fn getgeneration ,
and
.Fn getversion
return the indicated \fBsysctl\fR variable, or -1 if there is an error
fetching the variable.
.Pp
.Fn checkversion
returns 0 if the kernel and userland
.Nm devstat
versions match.  If they do not match, it returns -1.
.Pp
.Fn getdevs
and
.Fn selectdevs
return -1 in case of an error, 0 if there is no error and 1 if the device
list or selected devices have changed.  A return value of 1 from
.Fn getdevs
is usually a hint to re-run
.Fn selectdevs
because the device list has changed.
.Pp
.Fn buildmatch
returns -1 for error, and 0 if there is no error.
.Pp
.Fn compute_stats
returns -1 for error, and 0 for success.
.Pp
.Fn compute_etime
returns the computed elapsed time.
.Pp
If an error is returned from one of the
.Nm
library functions, the reason for the error is generally printed in
the global string
.Va devstat_errbuf
which is
.Dv DEVSTAT_ERRBUF_SIZE
characters long.
.Sh SEE ALSO
.Xr systat 1 ,
.Xr iostat 8 ,
.Xr rpc.rstatd 8 ,
.Xr vmstat 8 ,
.Xr devstat 9
.Sh HISTORY
The
.Nm
statistics system first appeared in
.Fx 3.0 .
.Sh AUTHORS
.An Kenneth Merry Aq ken@FreeBSD.ORG
.Sh BUGS
There should probably be an interface to de-allocate memory allocated by
.Fn getdevs ,
.Fn selectdevs ,
and
.Fn buildmatch .
.Pp
.Fn selectdevs
should probably not select more than
.Va maxshowdevs
devices in
.Dq top
mode when no devices have been selected previously.
.Pp
There should probably be functions to perform the statistics buffer
swapping that goes on in most of the clients of this library.
.Pp
The
.Va statinfo
and
.Va devinfo
structures should probably be cleaned up and thought out a little more.
OpenPOWER on IntegriCloud