1fx_dptbl(4) File Formats fx_dptbl(4)
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6 fx_dptbl - fixed priority dispatcher parameter table
7
9 fx_dptbl
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13 The process scheduler or dispatcher is the portion of the kernel that
14 controls allocation of the CPU to processes. The scheduler supports the
15 notion of scheduling classes, where each class defines a scheduling
16 policy used to schedule processes within that class. Associated with
17 each scheduling class is a set of priority queues on which ready-to-run
18 processes are linked. These priority queues are mapped by the system
19 configuration into a set of global scheduling priorities, which are
20 available to processes within the class. The dispatcher always selects
21 for execution the process with the highest global scheduling priority
22 in the system. The priority queues associated with a given class are
23 viewed by that class as a contiguous set of priority levels numbered
24 from 0 (lowest priority) to n (highest priority—a configuration-depen‐
25 dent value). The set of global scheduling priorities that the queues
26 for a given class are mapped into might not start at zero and might not
27 be contiguous, depending on the configuration.
28 Processes in the fixed priority class are scheduled according to the
31 parameters in a fixed-priority dispatcher parameter table (fx_dptbl).
32 The fx_dptbl table consists of an array (config_fx_dptbl[]) of parame‐
33 ter structures (struct fxdpent_t), one for each of the n priority lev‐
34 els used by fixed priority processes in user mode. The structures are
35 accessed by way of a pointer, (fx_dptbl), to the array. The properties
36 of a given priority level i are specified by the ith parameter struc‐
37 ture in this array (fx_dptbl[i]).
38 A parameter structure consists of the following members. These are also
41 described in the /usr/include/sys/fx.h header.
42 fx_globpri The global scheduling priority associated with this pri‐
44 ority level. The mapping between fixed-priority priority
45 levels and global scheduling priorities is determined at
46 boot time by the system configuration. fx_globpri can not
47 be changed with dispadmin(1M).
48 fx_quantum The length of the time quantum allocated to processes at
51 this level in ticks (hz). The time quantum value is only
52 a default or starting value for processes at a particular
53 level, as the time quantum of a fixed priority process
54 can be changed by the user with the priocntl(1) command
55 or the priocntl(2) system call.
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 An administrator can affect the behavior of the fixed
62 priority portion of the scheduler by reconfiguring the
63 fx_dptbl. There are two methods available for doing this:
64 reconfigure with a loadable module at boot-time or by
65 using dispadmin(1M) at run-time.
66 fx_dptbl Loadable Module
69 The fx_dptbl can be reconfigured with a loadable module that contains a
70 new fixed priority dispatch table. The module containing the dispatch
71 table is separate from the FX loadable module, which contains the rest
72 of the fixed priority software. This is the only method that can be
73 used to change the number of fixed priority priority levels or the set
74 of global scheduling priorities used by the fixed priority class. The
75 relevant procedure and source code is described in Replacing the
76 fx_dptbl Loadable Module below.
77 dispadmin Configuration File
79 The fx_quantum values in the fx_dptbl can be examined and modified on a
80 running system using the dispadmin(1M) command. Invoking dispadmin for
81 the fixed-priority class allows the administrator to retrieve the cur‐
82 rent fx_dptbl configuration from the kernel's in-core table or over‐
83 write the in-core table with values from a configuration file. The con‐
84 figuration file used for input to dispadmin must conform to the spe‐
85 cific format described as follows:
86 o Blank lines are ignored and any part of a line to the right
88 of a # symbol is treated as a comment.
89 o The first non-blank, non-comment line must indicate the res‐
91 olution to be used for interpreting the time quantum values.
92 The resolution is specified as:
93 RES=res
95 where res is a positive integer between 1 and 1,000,000,000
98 inclusive and the resolution used is the reciprocal of res
99 in seconds (for example, RES=1000 specifies millisecond res‐
100 olution). Although you can specify very fine (nanosecond)
101 resolution, the time quantum lengths are rounded up to the
102 next integral multiple of the system clock's resolution.
103 o The remaining lines in the file are used to specify the
105 fx_quantum values for each of the fixed-priority priority
106 levels. The first line specifies the quantum for fixed-pri‐
107 ority level 0, the second line specifies the quantum for
108 fixed-priority level 1, and so forth. There must be exactly
109 one line for each configured fixed priority priority level.
110 Each fx_quantum entry must be a positive integer specifying
111 the desired time quantum in the resolution given by res.
112 See Examples for an example of an excerpt of a dispadmin configuration
115 file.
116 Replacing the fx_dptbl Loadable Module
118 To change the size of the fixed priority dispatch table, you must build
119 the loadable module that contains the dispatch table information. Save
120 the existing module before using the following procedure.
121 1. Place the dispatch table code shown below in a file called
123 fx_dptbl.c. See EXAMPLES, below, for an example of this
124 file.
125 2. Compile the code using the given compilation and link lines
127 supplied:
128 cc -c -0 -D_KERNEL fx_dptbl.c
130 ld -r -o FX_DPTBL fx_dptbl.o
131 3. Copy the current dispatch table in /usr/kernel/sched to
135 FX_DPTBL.bak.
136 4. Replace the current FX_DPTBL in /usr/kernel/sched.
138 5. Make changes in the /etc/system file to reflect the changes
140 to the sizes of the tables. See system(4). The variables
141 affected is fx_maxupri. The syntax for setting this is as
142 follows:
143 set FX:fx_maxupri=(value for max fixed-priority user priority)
145 6. Reboot the system to use the new dispatch table.
149 Exercise great care in using the preceding method to replace the dis‐
152 patch table. A mistake can result in panics, thus making the system
153 unusable.
154
156 Example 1 Configuration File Excerpt
157 The following excerpt from a dispadmin configuration file illustrates
160 the correct format. Note that, for each line specifying a set of param‐
161 eters, there is a comment indicating the corresponding priority level.
162 These level numbers indicate priority within the fixed priority class;
163 the mapping between these fixed-priority priorities and the correspond‐
164 ing global scheduling priorities is determined by the configuration
165 specified in the FX_DPTBL loadable module. The level numbers are
166 strictly for the convenience of the administrator reading the file and,
167 as with any comment, they are ignored by dispadmin. The dispadmin com‐
168 mand assumes that the lines in the file are ordered by consecutive,
169 increasing priority level (from 0 to the maximum configured fixed-pri‐
170 ority priority). For the sake of someone reading the file, the level
171 numbers in the comments should agree with this ordering. If for some
172 reason they do not, dispadmin is unaffected.
173 # Fixed Priority Dispatcher Configuration File RES=1000
176 RES=1000
178 # TIME QUANTUM PRIORITY
179 # (fx_quantum) LEVEL
180 200 # 0
181 200 # 1
182 200 # 2
183 200 # 3
184 200 # 4
185 200 # 5
186 200 # 6
187 200 # 7
188 . . .
189 . . .
190 . . .
191 20 # 58
192 20 # 59
193 20 # 60
194 Example 2 fx_dptbl.c File Used for Building the New fx_dptbl
198 The following is an example of a fx_dptbl.c file used for building the
201 new fx_dptbl.
202 /* BEGIN fx_dptbl.c */
205 #include <sys/proc.h>
207 #include <sys/priocntl.h>
208 #include <sys/class.h>
209 #include <sys/disp.h>
210 #include <sys/fx.h>
211 #include <sys/fxpriocntl.h>
212 /*
215 * This is the loadable module wrapper.
216 */
217 #include <sys/modctl.h>
219 extern struct mod_ops mod_miscops;
221 /*
223 * Module linkage information for the kernel.
224 */
225 static struct modlmisc modlmisc = {
227 &mod_miscops, "Fixed priority dispatch table"
228 };
229 static struct modlinkage modlinkage = {
231 MODREV_1, &modlmisc, 0
232 };
233 _init()
235 {
236 return (mod_install(&modlinkage));
237 }
238 _info(modinfop)
240 struct modinfo *modinfop;
241 {
242 return (mod_info(&modlinkage, modinfop));
243 }
244 #define FXGPUP0 0 /* Global priority for FX user priority 0 */
246 fxdpent_t config_fx_dptbl[] = {
247 /* glbpri qntm */
249 FXGPUP0+0, 20,
251 FXGPUP0+1, 20,
252 FXGPUP0+2, 20,
253 FXGPUP0+3, 20,
254 FXGPUP0+4, 20,
255 FXGPUP0+5, 20,
256 FXGPUP0+6, 20,
257 FXGPUP0+7, 20,
258 FXGPUP0+8, 20,
259 FXGPUP0+9, 20,
260 FXGPUP0+10, 16,
261 FXGPUP0+11, 16,
262 FXGPUP0+12, 16,
263 FXGPUP0+13, 16,
264 FXGPUP0+14, 16,
265 FXGPUP0+15, 16,
266 FXGPUP0+16, 16,
267 FXGPUP0+17, 16,
268 FXGPUP0+18, 16,
269 FXGPUP0+19, 16,
270 FXGPUP0+20, 12,
271 FXGPUP0+21, 12,
272 FXGPUP0+22, 12,
273 FXGPUP0+23, 12,
274 FXGPUP0+24, 12,
275 FXGPUP0+25, 12,
276 FXGPUP0+26, 12,
277 FXGPUP0+27, 12,
278 FXGPUP0+28, 12,
279 FXGPUP0+29, 12,
280 FXGPUP0+30, 8,
281 FXGPUP0+31, 8,
282 FXGPUP0+32, 8,
283 FXGPUP0+33, 8,
284 FXGPUP0+34, 8,
285 FXGPUP0+35, 8,
286 FXGPUP0+36, 8,
287 FXGPUP0+37, 8,
288 FXGPUP0+38, 8,
289 FXGPUP0+39, 8,
290 FXGPUP0+40, 4,
291 FXGPUP0+41, 4,
292 FXGPUP0+42, 4,
293 FXGPUP0+43, 4,
294 FXGPUP0+44, 4,
295 FXGPUP0+45, 4,
296 FXGPUP0+46, 4,
297 FXGPUP0+47, 4,
298 FXGPUP0+48, 4,
299 FXGPUP0+49, 4,
300 FXGPUP0+50, 4,
301 FXGPUP0+51, 4,
302 FXGPUP0+52, 4,
303 FXGPUP0+53, 4,
304 FXGPUP0+54, 4,
305 FXGPUP0+55, 4,
306 FXGPUP0+56, 4,
307 FXGPUP0+57, 4,
308 FXGPUP0+58, 4,
309 FXGPUP0+59, 2,
310 FXGPUP0+60 2,
311 };
312 pri_t config_fx_maxumdpri =
316 sizeof (config_fx_dptbl) / sizeof (fxdpent_t) - 1;
317 /*
319 * Return the address of config_fx_dptbl
320 */
321 fxdpent_t *
322 fx_getdptbl()
323 {
324 return (config_fx_dptbl);
325 }
326 /*
328 * Return the address of fx_maxumdpri
329 */
330 pri_t
331 fx_getmaxumdpri()
332 {
333 /*
334 * the config_fx_dptbl table.
335 */
336 return (config_fx_maxumdpri);
337 }
338
342 priocntl(1), dispadmin(1M), priocntl(2), system(4)
343 System Administration Guide, Volume 1, System Interface Guide
346
348 In order to improve performance under heavy system load, both the nfsd
349 daemon and the lockd daemon utilize the maximum priority in the FX
350 class. Unusual fx_dptbl configurations may have significant negative
351 impact on the performance of the nfsd and lockd daemons.
352SunOS 5.11 15 Oct 2002 fx_dptbl(4)