File Formats fx_dptbl(4)
NAME
fx_dptbl - fixed priority dispatcher parameter table
SYNOPSIS
fx_dptbl
DESCRIPTION
The process scheduler or dispatcher is the portion of the kernel that controls allocation of the CPU to processes. The scheduler supports the notion of scheduling classes, where each class defines a scheduling policy used to schedule processes within that class. Associated with each schedulingclass is a set of priority queues on which ready-to-run
processes are linked. These priority queues are mapped by the system configuration into a set of global scheduling priorities, which are available to processes within theclass. The dispatcher always selects for execution the pro-
cess with the highest global scheduling priority in the sys-
tem. The priority queues associated with a given class are viewed by that class as a contiguous set of priority levelsnumbered from 0 (lowest priority) to n (highest priority-a
configuration-dependent value). The set of global scheduling
priorities that the queues for a given class are mapped intomight not start at zero and might not be contiguous, depend-
ing on the configuration.Processes in the fixed priority class are scheduled accord-
ing to the parameters in a fixed-priority dispatcher parame-
ter table (fx_dptbl). The fx_dptbl table consists of an
array (config_fx_dptbl[]) of parameter structures (struct
fxdpent_t), one for each of the n priority levels used by
fixed priority processes in user mode. The structures areaccessed by way of a pointer, (fx_dptbl), to the array. The
properties of a given priority level i are specified by theith parameter structure in this array (fx_dptbl[i]).
A parameter structure consists of the following members. These are also described in the /usr/include/sys/fx.h header.fx_globpri The global scheduling priority associated with
this priority level. The mapping betweenfixed-priority priority levels and global
scheduling priorities is determined at boottime by the system configuration. fx_globpri
can not be changed with dispadmin(1M).SunOS 5.11 Last change: 15 Oct 2002 1
File Formats fx_dptbl(4)
fx_quantum The length of the time quantum allocated to
processes at this level in ticks (hz). Thetime quantum value is only a default or start-
ing value for processes at a particular level,as the time quantum of a fixed priority pro-
cess can be changed by the user with the priocntl(1) command or the priocntl(2) system call.In the high resolution clock mode (hires_tick
set to 1), the value of hz is set to 1000.Increase quantums to maintain the same abso-
lute time quantums. An administrator can affect the behavior of the fixed priority portion of the scheduler byreconfiguring the fx_dptbl. There are two
methods available for doing this: reconfigurewith a loadable module at boot-time or by
using dispadmin(1M) at run-time.
fx_dptbl Loadable Module
The fx_dptbl can be reconfigured with a loadable module that
contains a new fixed priority dispatch table. The modulecontaining the dispatch table is separate from the FX load-
able module, which contains the rest of the fixed priority software. This is the only method that can be used to change the number of fixed priority priority levels or the set of global scheduling priorities used by the fixed priority class. The relevant procedure and source code is describedin Replacing the fx_dptbl Loadable Module below.
dispadmin Configuration FileThe fx_quantum values in the fx_dptbl can be examined and
modified on a running system using the dispadmin(1M) com-
mand. Invoking dispadmin for the fixed-priority class allows
the administrator to retrieve the current fx_dptbl confi-
guration from the kernel's in-core table or overwrite the
in-core table with values from a configuration file. The
configuration file used for input to dispadmin must conform to the specific format described as follows: o Blank lines are ignored and any part of a line tothe right of a # symbol is treated as a comment.
o The first non-blank, non-comment line must indicate
the resolution to be used for interpreting the time quantum values. The resolution is specified as: RES=resSunOS 5.11 Last change: 15 Oct 2002 2
File Formats fx_dptbl(4)
where res is a positive integer between 1 and 1,000,000,000 inclusive and the resolution used is the reciprocal of res in seconds (for example, RES=1000 specifies millisecond resolution). Although you can specify very fine (nanosecond) resolution, the time quantum lengths are rounded up to the next integral multiple of the system clock's resolution. o The remaining lines in the file are used to specifythe fx_quantum values for each of the fixed-
priority priority levels. The first line specifiesthe quantum for fixed-priority level 0, the second
line specifies the quantum for fixed-priority level
1, and so forth. There must be exactly one line for each configured fixed priority priority level. Eachfx_quantum entry must be a positive integer speci-
fying the desired time quantum in the resolution given by res. See Examples for an example of an excerpt of a dispadmin configuration file.Replacing the fx_dptbl Loadable Module
To change the size of the fixed priority dispatch table, you must build the loadable module that contains the dispatch table information. Save the existing module before using the following procedure. 1. Place the dispatch table code shown below in a filecalled fx_dptbl.c. See EXAMPLES, below, for an
example of this file. 2. Compile the code using the given compilation and link lines supplied:cc -c -0 -D_KERNEL fx_dptbl.c
ld -r -o FX_DPTBL fx_dptbl.o
3. Copy the current dispatch table in/usr/kernel/sched to FX_DPTBL.bak.
4. Replace the current FX_DPTBL in /usr/kernel/sched.
5. Make changes in the /etc/system file to reflect the changes to the sizes of the tables. See system(4).The variables affected is fx_maxupri. The syntax
for setting this is as follows:SunOS 5.11 Last change: 15 Oct 2002 3
File Formats fx_dptbl(4)
set FX:fx_maxupri=(value for max fixed-priority user priority)
6. Reboot the system to use the new dispatch table. Exercise great care in using the preceding method to replace the dispatch table. A mistake can result in panics, thus making the system unusable.EXAMPLES
Example 1 Configuration File Excerpt The following excerpt from a dispadmin configuration file illustrates the correct format. Note that, for each linespecifying a set of parameters, there is a comment indicat-
ing the corresponding priority level. These level numbersindicate priority within the fixed priority class; the map-
ping between these fixed-priority priorities and the
corresponding global scheduling priorities is determined bythe configuration specified in the FX_DPTBL loadable module.
The level numbers are strictly for the convenience of the administrator reading the file and, as with any comment, they are ignored by dispadmin. The dispadmin command assumes that the lines in the file are ordered by consecutive, increasing priority level (from 0 to the maximum configuredfixed-priority priority). For the sake of someone reading
the file, the level numbers in the comments should agreewith this ordering. If for some reason they do not, dispad-
min is unaffected.# Fixed Priority Dispatcher Configuration File RES=1000
RES=1000# TIME QUANTUM PRIORITY
# (fx_quantum) LEVEL
200 # 0
200 # 1
200 # 2
200 # 3
200 # 4
200 # 5
200 # 6
200 # 7
. . . . . . . . .20 # 58
20 # 59
SunOS 5.11 Last change: 15 Oct 2002 4
File Formats fx_dptbl(4)
20 # 60
Example 2 fx_dptbl.c File Used for Building the New fx_dptbl
The following is an example of a fx_dptbl.c file used for
building the new fx_dptbl.
/* BEGIN fx_dptbl.c */
#include
#include
#include
#include
#include
#include
/* * This is the loadable module wrapper. */#include
extern struct mod_ops mod_miscops;
/* * Module linkage information for the kernel. */ static struct modlmisc modlmisc = {&mod_miscops, "Fixed priority dispatch table"
}; static struct modlinkage modlinkage = {MODREV_1, &modlmisc, 0
};_init()
{return (mod_install(&modlinkage));
}_info(modinfop)
struct modinfo *modinfop; {return (mod_info(&modlinkage, modinfop));
}SunOS 5.11 Last change: 15 Oct 2002 5
File Formats fx_dptbl(4)
#define FXGPUP0 0 /* Global priority for FX user priority 0 */
fxdpent_t config_fx_dptbl[] = {
/* glbpri qntm */ FXGPUP0+0, 20, FXGPUP0+1, 20, FXGPUP0+2, 20, FXGPUP0+3, 20, FXGPUP0+4, 20, FXGPUP0+5, 20, FXGPUP0+6, 20, FXGPUP0+7, 20, FXGPUP0+8, 20, FXGPUP0+9, 20, FXGPUP0+10, 16, FXGPUP0+11, 16, FXGPUP0+12, 16, FXGPUP0+13, 16, FXGPUP0+14, 16, FXGPUP0+15, 16, FXGPUP0+16, 16, FXGPUP0+17, 16, FXGPUP0+18, 16, FXGPUP0+19, 16, FXGPUP0+20, 12, FXGPUP0+21, 12, FXGPUP0+22, 12, FXGPUP0+23, 12, FXGPUP0+24, 12, FXGPUP0+25, 12, FXGPUP0+26, 12, FXGPUP0+27, 12, FXGPUP0+28, 12, FXGPUP0+29, 12, FXGPUP0+30, 8, FXGPUP0+31, 8, FXGPUP0+32, 8, FXGPUP0+33, 8, FXGPUP0+34, 8, FXGPUP0+35, 8, FXGPUP0+36, 8, FXGPUP0+37, 8, FXGPUP0+38, 8, FXGPUP0+39, 8, FXGPUP0+40, 4, FXGPUP0+41, 4, FXGPUP0+42, 4, FXGPUP0+43, 4, FXGPUP0+44, 4, FXGPUP0+45, 4, FXGPUP0+46, 4,SunOS 5.11 Last change: 15 Oct 2002 6
File Formats fx_dptbl(4)
FXGPUP0+47, 4, FXGPUP0+48, 4, FXGPUP0+49, 4, FXGPUP0+50, 4, FXGPUP0+51, 4, FXGPUP0+52, 4, FXGPUP0+53, 4, FXGPUP0+54, 4, FXGPUP0+55, 4, FXGPUP0+56, 4, FXGPUP0+57, 4, FXGPUP0+58, 4, FXGPUP0+59, 2, FXGPUP0+60 2, };pri_t config_fx_maxumdpri =
sizeof (config_fx_dptbl) / sizeof (fxdpent_t) - 1;
/** Return the address of config_fx_dptbl
*/fxdpent_t *
fx_getdptbl()
{return (config_fx_dptbl);
} /** Return the address of fx_maxumdpri
*/pri_t
fx_getmaxumdpri()
{ /** the config_fx_dptbl table.
*/return (config_fx_maxumdpri);
}SEE ALSO
priocntl(1), dispadmin(1M), priocntl(2), system(4) System Administration Guide, Volume 1, System Interface GuideSunOS 5.11 Last change: 15 Oct 2002 7
File Formats fx_dptbl(4)
NOTES In order to improve performance under heavy system load,both the nfsd daemon and the lockd daemon utilize the max-
imum priority in the FX class. Unusual fx_dptbl configura-
tions may have significant negative impact on the perfor-
mance of the nfsd and lockd daemons.SunOS 5.11 Last change: 15 Oct 2002 8