1ts_dptbl(4) File Formats ts_dptbl(4)
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6 ts_dptbl - time-sharing dispatcher parameter table
7
9 The process scheduler (or dispatcher) is the portion of the kernel that
10 controls allocation of the CPU to processes. The scheduler supports the
11 notion of scheduling classes where each class defines a scheduling pol‐
12 icy, used to schedule processes within that class. Associated with each
13 scheduling class is a set of priority queues on which ready to run pro‐
14 cesses are linked. These priority queues are mapped by the system con‐
15 figuration into a set of global scheduling priorities which are avail‐
16 able to processes within the class. (The dispatcher always selects for
17 execution the process with the highest global scheduling priority in
18 the system.) The priority queues associated with a given class are
19 viewed by that class as a contiguous set of priority levels numbered
20 from 0 (lowest priority) to n (highest priority—a configuration-depen‐
21 dent value). The set of global scheduling priorities that the queues
22 for a given class are mapped into might not start at zero and might not
23 be contiguous (depending on the configuration).
24 Processes in the time-sharing class which are running in user mode (or
27 in kernel mode before going to sleep) are scheduled according to the
28 parameters in a time-sharing dispatcher parameter table (ts_dptbl).
29 Processes in the inter-active scheduling class are also scheduled
30 according to the parameters in the time-sharing dispatcher parameter
31 table. (Time-sharing processes and inter-active processes running in
32 kernel mode after sleeping are run within a special range of priorities
33 reserved for such processes and are not affected by the parameters in
34 the ts_dptbl until they return to user mode.) The ts_dptbl consists of
35 an array (config_ts_dptbl[]) of parameter structures (struct tsd‐
36 pent_t), one for each of the n priority levels used by time-sharing
37 processes and inter-active processes in user mode. The structures are
38 accessed via a pointer, (ts_dptbl), to the array. The properties of a
39 given priority level i are specified by the ith parameter structure in
40 this array (ts_dptbl[ i] ).
41 A parameter structure consists of the following members. These are also
44 described in the /usr/include/sys/ts.h header.
45 ts_globpri The global scheduling priority associated with this pri‐
47 ority level. The mapping between time-sharing priority
48 levels and global scheduling priorities is determined at
49 boot time by the system configuration. ts_globpri is the
50 only member of the ts_dptbl which cannot be changed with
51 dispadmin(1M).
52 ts_quantum The length of the time quantum allocated to processes at
55 this level in ticks (hz).
56 In the high resolution clock mode (hires_tick set to 1),
58 the value of hz is set to 1000. Increase quantums to
59 maintain the same absolute time quantums.
60 ts_tqexp Priority level of the new queue on which to place a
63 process running at the current level if it exceeds its
64 time quantum. Normally this field links to a lower prior‐
65 ity time-sharing level that has a larger quantum.
66 ts_slpret Priority level of the new queue on which to place a
69 process, that was previously in user mode at this level,
70 when it returns to user mode after sleeping. Normally
71 this field links to a higher priority level that has a
72 smaller quantum.
73 ts_maxwait A per process counter, ts_dispwait is initialized to zero
76 each time a time-sharing or inter-active process is
77 placed back on the dispatcher queue after its time quan‐
78 tum has expired or when it is awakened (ts_dispwait is
79 not reset to zero when a process is preempted by a higher
80 priority process). This counter is incremented once per
81 second for each process on a dispatcher or sleep queue.
82 If a process' ts_dispwait value exceeds the ts_maxwait
83 value for its level, the process' priority is changed to
84 that indicated by ts_lwait. The purpose of this field is
85 to prevent starvation.
86 ts_lwait Move a process to this new priority level if ts_dispwait
89 is greater than ts_maxwait.
90 An administrator can affect the behavior of the time-sharing portion of
94 the scheduler by reconfiguring the ts_dptbl. Since processes in the
95 time-sharing and inter-active scheduling classes share the same dis‐
96 patch parameter table (ts_dptbl), changes to this table will affect
97 both scheduling classes. There are two methods available for doing
98 this: reconfigure with a loadable module at boot-time or by using dis‐
99 padmin(1M) at run-time.
100 ts_dptbl Loadable Module
102 The ts_dptbl can be reconfigured with a loadable module which contains
103 a new time sharing dispatch table. The module containing the dispatch
104 table is separate from the TS loadable module which contains the rest
105 of the time-sharing and inter-active software. This is the only method
106 that can be used to change the number of time-sharing priority levels
107 or the set of global scheduling priorities used by the time-sharing and
108 inter-active classes. The relevant procedure and source code is
109 described in the REPLACING THE TS_DPTBL LOADABLE MODULE section.
110 dispadmin Configuration File
112 With the exception of ts_globpri all of the members of the ts_dptbl can
113 be examined and modified on a running system using the dispadmin(1M)
114 command. Invoking dispadmin for the time-sharing or inter-active class
115 allows the administrator to retrieve the current ts_dptbl configuration
116 from the kernel's in-core table, or overwrite the in-core table with
117 values from a configuration file. The configuration file used for input
118 to dispadmin must conform to the specific format described below.
119 Blank lines are ignored and any part of a line to the right of a # sym‐
122 bol is treated as a comment. The first non-blank, non-comment line must
123 indicate the resolution to be used for interpreting the ts_quantum time
124 quantum values. The resolution is specified as
125 RES=res
127 where res is a positive integer between 1 and 1,000,000,000 inclusive
131 and the resolution used is the reciprocal of res in seconds (for exam‐
132 ple, RES=1000 specifies millisecond resolution). Although very fine
133 (nanosecond) resolution may be specified, the time quantum lengths are
134 rounded up to the next integral multiple of the system clock's resolu‐
135 tion.
136 The remaining lines in the file are used to specify the parameter val‐
139 ues for each of the time-sharing priority levels. The first line speci‐
140 fies the parameters for time-sharing level 0, the second line specifies
141 the parameters for time-sharing level 1, etc. There must be exactly one
142 line for each configured time-sharing priority level.
143
145 Example 1 A Sample From a Configuration File
146 The following excerpt from a dispadmin configuration file illustrates
149 the format. Note that for each line specifying a set of parameters
150 there is a comment indicating the corresponding priority level. These
151 level numbers indicate priority within the time-sharing and interactive
152 classes, and the mapping between these time-sharing priorities and the
153 corresponding global scheduling priorities is determined by the config‐
154 uration specified in the ts master file. The level numbers are strictly
155 for the convenience of the administrator reading the file and, as with
156 any comment, they are ignored by dispadmin. dispadmin assumes that the
157 lines in the file are ordered by consecutive, increasing priority level
158 (from 0 to the maximum configured time-sharing priority). The level
159 numbers in the comments should normally agree with this ordering; if
160 for some reason they don't, however, dispadmin is unaffected.
161 # Time-Sharing Dispatcher Configuration File RES=1000
164 # ts_quantum ts_tqexp ts_slpret ts_maxwait ts_lwait PRIORITY
167 # LEVEL
168 500 0 10 5 10 # 0
169 500 0 11 5 11 # 1
170 500 1 12 5 12 # 2
171 500 1 13 5 13 # 3
172 500 2 14 5 14 # 4
173 500 2 15 5 15 # 5
174 450 3 16 5 16 # 6
175 450 3 17 5 17 # 7
176 . . . . . . .
177 . . . . . . .
178 . . . . . . .
179 50 48 59 5 59 # 58
180 50 49 59 5 59 # 59
181 Example 2 Replacing The ts_dptbl Loadable Module
184 In order to change the size of the time sharing dispatch table, the
187 loadable module which contains the dispatch table information will have
188 to be built. It is recommended that you save the existing module before
189 using the following procedure.
190 1. Place the dispatch table code shown below in a file called
193 ts_dptbl.c An example of this file follows.
194 2. Compile the code using the given compilation and link lines
196 supplied.
197 cc -c -0 -D_KERNEL
199 ts_dptbl.c
200 ld -r -o TS_DPTBL ts_dptbl.o
201 3. Copy the current dispatch table in /kernel/sched to
205 TS_DPTBL.bak.
206 4. Replace the current TS_DPTBL in /kernel/sched.
208 5. You will have to make changes in the /etc/system file to
210 reflect the changes to the sizes of the tables. See sys‐
211 tem(4). The two variables affected are ts_maxupri and
212 ts_maxkmdpri. The syntax for setting these is as follows:
213 set TS:ts_maxupri=(value for max time-sharing user priority)
215 set TS:ts_maxkmdpri=(number of kernel mode priorities - 1)
216 6. Reboot the system to use the new dispatch table.
220 Great care should be used in replacing the dispatch table using this
223 method. If you do not get it right, panics may result, thus making the
224 system unusable.
225 The following is an example of a ts_dptbl.c file used for building the
229 new ts_dptbl.
230 /* BEGIN ts_dptbl.c */
233 #include <sys/proc.h>
234 #include <sys/priocntl.h>
235 #include <sys/class.h>
236 #include <sys/disp.h>
237 #include <sys/ts.h>
238 #include <sys/rtpriocntl.h>
239 /*
240 * This is the loadable module wrapper.
241 */
242 #include <sys/modctl.h>
243 extern struct mod_ops mod_miscops;
244 /*
245 * Module linkage information for the kernel.
246 */
247 static struct modlmisc modlmisc = {
248 &mod_miscops, "Time sharing dispatch table"
249 };
250 static struct modlinkage modlinkage = {
251 MODREV_1, &modlmisc, 0
252 };
253 _init()
254 {
255 return (mod_install(&modlinkage));
256 }
257 _info(modinfop)
258 struct modinfo *modinfop;
259 {
260 return (mod_info(&modlinkage, modinfop));
261 }
262 /*
263 * array of global priorities used by ts procs sleeping or
264 * running in kernel mode after sleep. Must have at least
265 * 40 values.
266 */
267 pri_t config_ts_kmdpris[] = {
268 60,61,62,63,64,65,66,67,68,69,
269 70,71,72,73,74,75,76,77,78,79,
270 80,81,82,83,84,85,86,87,88,89,
271 90,91,92,93,94,95,96,97,98,99,
272 };
273 tsdpent_t config_ts_dptbl[] = {
274 /* glbpri qntm tqexp slprt mxwt lwt */
276 0, 100, 0, 10, 5, 10,
278 1, 100, 0, 11, 5, 11,
279 2, 100, 1, 12, 5, 12,
280 3, 100, 1, 13, 5, 13,
281 4, 100, 2, 14, 5, 14
282 5, 100, 2, 15, 5, 15,
283 6, 100, 3, 16, 5, 16,
284 7, 100, 3, 17, 5, 17,
285 8, 100, 4, 18, 5, 18,
286 9, 100, 4, 19, 5, 19,
287 10, 80, 5, 20, 5, 20,
288 11, 80, 5, 21, 5, 21,
289 12, 80, 6, 22, 5, 22,
290 13, 80, 6, 23, 5, 23,
291 14, 80, 7, 24, 5, 24,
292 15, 80, 7, 25, 5, 25,
293 16, 80, 8, 26, 5, 26,
294 17, 80, 8, 27, 5, 27,
295 18, 80, 9, 28, 5, 28,
296 19, 80, 9, 29, 5, 29,
297 20, 60, 10, 30, 5, 30,
298 21, 60, 11, 31, 5, 31,
299 22, 60, 12, 32, 5, 33,
300 24, 60, 14, 34, 5, 34,
301 25, 60, 15, 35, 5, 35,
302 26, 60, 16, 36, 5, 36,
303 27, 60, 17, 37, 5, 37,
304 28, 60, 18, 38, 5, 38,
305 29, 60, 19, 39, 5, 39,
306 30, 40, 20, 40, 5, 40,
307 31, 40, 21, 41, 5, 41,
308 32, 40, 22, 42, 5, 42,
309 33, 40, 23, 43, 5, 43,
310 34, 40, 24, 44, 5, 44,
311 35, 40, 25, 45, 5, 45,
312 36, 40, 26, 46, 5, 46,
313 37, 40, 27, 47, 5, 47,
314 38, 40, 28, 48, 5, 48,
315 39, 40, 29, 49, 5, 49,
316 40, 20, 30, 50, 5, 50,
317 41, 20, 31, 50, 5, 50,
318 42, 20, 32, 51, 5, 51,
319 43, 20, 33, 51, 5, 51,
320 44, 20, 34, 52, 5, 52,
321 45, 20, 35, 52, 5, 52,
322 46, 20, 36, 53, 5, 53,
323 47, 20 37, 53, 5, 53,
324 48, 20, 38, 54, 5, 54,
325 49, 20, 39, 54, 5, 54,
326 50, 10, 40, 55, 5, 55,
327 51, 10, 41, 55, 5, 55,
328 52, 10, 42, 56, 5, 56,
329 53, 10, 43, 56, 5, 56,
330 54, 10, 44, 57, 5, 57,
331 55, 10, 45, 57, 5, 57,
332 56, 10, 46, 58, 5, 58,
333 57, 10, 47, 58, 5, 58,
334 58, 10, 48, 59, 5, 59,
335 59, 10, 49, 59, 5, 59,
336 };
338 short config_ts_maxumdpri = sizeof (config_ts_dptbl)/16 - 1;
340 /*
341 * Return the address of config_ts_dptbl
342 */
343 tsdpent_t *
344 ts_getdptbl()
345 {
346 return (config_ts_dptbl);
347 }
348 /*
350 * Return the address of config_ts_kmdpris
351 */
352 int *
353 ts_getkmdpris()
354 {
355 return (config_ts_kmdpris);
356 }
357 /*
359 * Return the address of ts_maxumdpri
360 */
361 short
362 ts_getmaxumdpri()
363 {
364 return (config_ts_maxumdpri);
365 }
366 /* END ts_dptbl.c */
368
371 priocntl(1), dispadmin(1M), priocntl(2), system(4)
372 System Administration Guide: Basic Administration
375 Programming Interfaces Guide
378
380 dispadmin does some limited sanity checking on the values supplied in
381 the configuration file. The sanity checking is intended to ensure that
382 the new ts_dptbl values do not cause the system to panic. The sanity
383 checking does not attempt to analyze the effect that the new values
384 will have on the performance of the system. Unusual ts_dptbl configura‐
385 tions may have a dramatic negative impact on the performance of the
386 system.
387 No sanity checking is done on the ts_dptbl values specified in the
390 TS_DPTBL loadable module. Specifying an inconsistent or nonsensical
391 ts_dptbl configuration through the TS_DPTBL loadable module could cause
392 serious performance problems and/or cause the system to panic.
393SunOS 5.11 15 Oct 2002 ts_dptbl(4)