File Formats fxdptbl(4)
NAME
fxdptbl - fixed priority dispatcher parameter table
SYNOPSIS
fxdptbl
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 scheduling
class 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 the
class. 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 levels
numbered 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 into
might 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 (fxdptbl). The fxdptbl table consists of an
array (configfxdptbl[]) of parameter structures (struct
fxdpentt), one for each of the n priority levels used by
fixed priority processes in user mode. The structures are
accessed by way of a pointer, (fxdptbl), to the array. The
properties of a given priority level i are specified by the
ith parameter structure in this array (fxdptbl[i]).
A parameter structure consists of the following members.
These are also described in the /usr/include/sys/fx.h
header.
fxglobpri The global scheduling priority associated with
this priority level. The mapping between
fixed-priority priority levels and global
scheduling priorities is determined at boot
time by the system configuration. fxglobpri
can not be changed with dispadmin(1M).
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fxquantum The length of the time quantum allocated to
processes at this level in ticks (hz). The
time 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 (hirestick
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 by
reconfiguring the fxdptbl. There are two
methods available for doing this: reconfigure
with a loadable module at boot-time or by
using dispadmin(1M) at run-time.
fxdptbl Loadable Module
The fxdptbl can be reconfigured with a loadable module that
contains a new fixed priority dispatch table. The module
containing 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 described
in Replacing the fxdptbl Loadable Module below.
dispadmin Configuration File
The fxquantum values in the fxdptbl 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 fxdptbl 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 to
the 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=res
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File Formats fxdptbl(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 specify
the fxquantum values for each of the fixed-
priority priority levels. The first line specifies
the 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. Each
fxquantum 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 fxdptbl 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 file
called fxdptbl.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 -DKERNEL fxdptbl.c
ld -r -o FXDPTBL fxdptbl.o
3. Copy the current dispatch table in
/usr/kernel/sched to FXDPTBL.bak.
4. Replace the current FXDPTBL 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 fxmaxupri. The syntax
for setting this is as follows:
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set FX:fxmaxupri=(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 line
specifying a set of parameters, there is a comment indicat-
ing the corresponding priority level. These level numbers
indicate priority within the fixed priority class; the map-
ping between these fixed-priority priorities and the
corresponding global scheduling priorities is determined by
the configuration specified in the FXDPTBL 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 configured
fixed-priority priority). For the sake of someone reading
the file, the level numbers in the comments should agree
with 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
# (fxquantum) LEVEL
200 # 0
200 # 1
200 # 2
200 # 3
200 # 4
200 # 5
200 # 6
200 # 7
. . .
. . .
. . .
20 # 58
20 # 59
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20 # 60
Example 2 fxdptbl.c File Used for Building the New fxdptbl
The following is an example of a fxdptbl.c file used for
building the new fxdptbl.
/* BEGIN fxdptbl.c */
#include
#include
#include
#include
#include
#include
/*
* This is the loadable module wrapper.
*/
#include
extern struct modops modmiscops;
/*
* Module linkage information for the kernel.
*/
static struct modlmisc modlmisc = {
&modmiscops, "Fixed priority dispatch table"
};
static struct modlinkage modlinkage = {
MODREV1, &modlmisc, 0
};
init()
{
return (modinstall(&modlinkage));
}
info(modinfop)
struct modinfo *modinfop;
{
return (modinfo(&modlinkage, modinfop));
}
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File Formats fxdptbl(4)
#define FXGPUP0 0 /* Global priority for FX user priority 0 */
fxdpentt configfxdptbl[] = {
/* 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,
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File Formats fxdptbl(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,
};
prit configfxmaxumdpri =
sizeof (configfxdptbl) / sizeof (fxdpentt) - 1;
/*
* Return the address of configfxdptbl
*/
fxdpentt *
fxgetdptbl()
{
return (configfxdptbl);
}
/*
* Return the address of fxmaxumdpri
*/
prit
fxgetmaxumdpri()
{
/*
* the configfxdptbl table.
*/
return (configfxmaxumdpri);
}
SEE ALSO
priocntl(1), dispadmin(1M), priocntl(2), system(4)
System Administration Guide, Volume 1, System Interface
Guide
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File Formats fxdptbl(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 fxdptbl configura-
tions may have significant negative impact on the perfor-
mance of the nfsd and lockd daemons.
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