path: root/usr/src/man/man4/ts_dptbl.4

'\" te
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.TH TS_DPTBL 4 "Oct 15, 2002"
.SH NAME
ts_dptbl \- time-sharing dispatcher parameter table
.SH DESCRIPTION
.sp
.LP
The process scheduler (or dispatcher) is the portion of the kernel that
controls allocation of the \fBCPU\fR 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 process with the highest global
scheduling priority in the system.) 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 \fIn\fR (highest priority\(ema
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 (depending on the configuration).
.sp
.LP
Processes in the time-sharing class which are running in user mode (or in
kernel mode before going to sleep) are scheduled according to the parameters in
a time-sharing dispatcher parameter table (\fBts_dptbl\fR). Processes in the
inter-active scheduling class are also scheduled according to the parameters in
the time-sharing dispatcher parameter table. (Time-sharing processes and
inter-active processes running in kernel mode after sleeping are run within a
special range of priorities reserved for such processes and are not affected by
the parameters in the \fBts_dptbl\fR until they return to user mode.) The
\fBts_dptbl\fR consists of an array (\fBconfig_ts_dptbl[]\fR) of parameter
structures (\fBstruct tsdpent_t\fR), one for each of the \fIn\fR priority
levels used by time-sharing processes and inter-active processes in user mode.
The structures are accessed via a pointer, (\fBts_dptbl\fR), to the array. The
properties of a given priority level \fIi\fR are specified by the \fIi\fRth
parameter structure in this array (\fBts_dptbl[\fR \fIi\fR\fB]\fR ).
.sp
.LP
A parameter structure consists of the following members. These are also
described in the \fB/usr/include/sys/ts.h\fR header.
.sp
.ne 2
.na
\fB\fBts_globpri\fR\fR
.ad
.RS 14n
The global scheduling priority associated with this priority level. The mapping
between time-sharing priority levels and global scheduling priorities is
determined at boot time by the system configuration. \fBts_globpri\fR is the
only member of the \fBts_dptbl\fR which cannot be changed with
\fBdispadmin\fR(1M).
.RE

.sp
.ne 2
.na
\fB\fBts_quantum\fR\fR
.ad
.RS 14n
The length of the time quantum allocated to processes at this level in ticks
(\fBhz\fR).
.sp
In the high resolution clock mode (\fBhires_tick\fR set to \fB1\fR), the value
of \fBhz\fR is set to \fB1000\fR. Increase quantums to maintain the same
absolute time quantums.
.RE

.sp
.ne 2
.na
\fB\fBts_tqexp\fR\fR
.ad
.RS 14n
Priority level of the new queue on which to place a process running at the
current level if it exceeds its time quantum. Normally this field links to a
lower priority time-sharing level that has a larger quantum.
.RE

.sp
.ne 2
.na
\fB\fBts_slpret\fR\fR
.ad
.RS 14n
Priority level of the new queue on which to place a process, that was
previously in user mode at this level, when it returns to user mode after
sleeping. Normally this field links to a higher priority level that has a
smaller quantum.
.RE

.sp
.ne 2
.na
\fB\fBts_maxwait\fR\fR
.ad
.RS 14n
A per process counter, \fBts_dispwait\fR is initialized to zero each time a
time-sharing or inter-active process is placed back on the dispatcher queue
after its time quantum has expired or when it is awakened (\fBts_dispwait\fR is
not reset to zero when a process is preempted by a higher priority process).
This counter is incremented once per second for each process on a dispatcher or
sleep queue. If a process' \fBts_dispwait\fR value exceeds the \fBts_maxwait\fR
value for its level, the process' priority is changed to that indicated by
\fBts_lwait\fR. The purpose of this field is to prevent starvation.
.RE

.sp
.ne 2
.na
\fB\fBts_lwait\fR\fR
.ad
.RS 14n
Move a process to this new priority level if \fBts_dispwait\fR is greater than
\fBts_maxwait\fR.
.RE

.sp
.LP
An administrator can affect the behavior of the time-sharing portion of the
scheduler by reconfiguring the \fBts_dptbl\fR. Since processes in the
time-sharing and inter-active scheduling classes share the same dispatch
parameter table (\fBts_dptbl\fR), changes to this table will affect both
scheduling classes. There are two methods available for doing this: reconfigure
with a loadable module at boot-time or by using \fBdispadmin\fR(1M) at
run-time.
.SS "ts_dptbl Loadable Module"
.sp
.LP
The \fBts_dptbl\fR can be reconfigured with a loadable module which contains a
new time sharing dispatch table. The module containing the dispatch table is
separate from the TS loadable module which contains the rest of the
time-sharing and inter-active software. This is the only method that can be
used to change the number of time-sharing priority levels or the set of global
scheduling priorities used by the time-sharing and inter-active classes. The
relevant procedure and source code is described in the \fBREPLACING THE
TS_DPTBL LOADABLE MODULE\fR section.
.SS "dispadmin Configuration File"
.sp
.LP
With the exception of \fBts_globpri\fR all of the members of the \fBts_dptbl\fR
can be examined and modified on a running system using the \fBdispadmin\fR(1M)
command. Invoking \fBdispadmin\fR for the time-sharing or inter-active class
allows the administrator to retrieve the current \fBts_dptbl\fR configuration
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
\fBdispadmin\fR must conform to the specific format described below.
.sp
.LP
Blank lines are ignored and any part of a line to the right of a \fI#\fR symbol
is treated as a comment. The first non-blank, non-comment line must indicate
the resolution to be used for interpreting the \fBts_quantum\fR time quantum
values. The resolution is specified as
.sp
.in +2
.nf
\fBRES=\fR\fIres\fR
.fi
.in -2

.sp
.LP
where \fIres\fR is a positive integer between 1 and 1,000,000,000 inclusive and
the resolution used is the reciprocal of \fIres\fR in seconds (for example,
\fBRES=1000\fR specifies millisecond resolution). Although very fine
(nanosecond) resolution may be specified, the time quantum lengths are rounded
up to the next integral multiple of the system clock's resolution.
.sp
.LP
The remaining lines in the file are used to specify the parameter values for
each of the time-sharing priority levels. The first line specifies the
parameters for time-sharing level 0, the second line specifies the parameters
for time-sharing level 1, etc. There must be exactly one line for each
configured time-sharing priority level.
.SH EXAMPLES
.LP
\fBExample 1 \fRA Sample From a Configuration File
.sp
.LP
The following excerpt from a \fBdispadmin\fR configuration file illustrates the
format. Note that for each line specifying a set of parameters there is a
comment indicating the corresponding priority level. These level numbers
indicate priority within the time-sharing and interactive classes, and the
mapping between these time-sharing priorities and the corresponding global
scheduling priorities is determined by the configuration specified in the
\fBts\fR master file. The level numbers are strictly for the convenience of the
administrator reading the file and, as with any comment, they are ignored by
\fBdispadmin\fR. \fBdispadmin\fR assumes that the lines in the file are ordered
by consecutive, increasing priority level (from 0 to the maximum configured
time-sharing priority). The level numbers in the comments should normally agree
with this ordering; if for some reason they don't, however, \fBdispadmin\fR is
unaffected.

.sp
.in +2
.nf
# Time-Sharing Dispatcher Configuration File RES=1000


# ts_quantum  ts_tqexp  ts_slpret  ts_maxwait  ts_lwait  PRIORITY
#                                                         LEVEL
500            0        10         5           10        # 0
500            0        11         5           11        # 1
500            1        12         5           12        # 2
500            1        13         5           13        # 3
500            2        14         5           14        # 4
500            2        15         5           15        # 5
450            3        16         5           16        # 6
450            3        17         5           17        # 7
\&.              .        .          .           .         . .
\&.              .        .          .           .         . .
\&.              .        .          .           .         . .
50             48       59         5           59        # 58
50             49       59         5           59        # 59
.fi
.in -2

.LP
\fBExample 2 \fRReplacing The ts_dptbl Loadable Module
.sp
.LP
In order to change the size of the time sharing dispatch table, the loadable
module which contains the dispatch table information will have to be built. It
is recommended that you save the existing module before using the following
procedure.

.RS +4
.TP
1.
Place the dispatch table code shown below in a file called \fBts_dptbl.c\fR
An example of this file follows.
.RE
.RS +4
.TP
2.
Compile the code using the given compilation and link lines supplied.
.sp
.in +2
.nf
cc -c -0 -D_KERNEL
ts_dptbl.c
ld -r -o TS_DPTBL ts_dptbl.o
.fi
.in -2
.sp

.RE
.RS +4
.TP
3.
Copy the current dispatch table in \fB/kernel/sched\fR to
\fBTS_DPTBL.bak\fR.
.RE
.RS +4
.TP
4.
Replace the current \fBTS_DPTBL\fR in \fB/kernel/sched\fR.
.RE
.RS +4
.TP
5.
You will have to make changes in the \fB/etc/system\fR file to reflect the
changes to the sizes of the tables. See \fBsystem\fR(4). The two variables
affected are \fBts_maxupri\fR and \fBts_maxkmdpri\fR. The syntax for setting
these is as follows:
.sp
.in +2
.nf
set TS:ts_maxupri=(value for max time-sharing user priority)
set TS:ts_maxkmdpri=(number of kernel mode priorities - 1)
.fi
.in -2
.sp

.RE
.RS +4
.TP
6.
Reboot the system to use the new dispatch table.
.RE
.sp
.LP
Great care should be used in replacing the dispatch table using this method. If
you do not get it right, panics may result, thus making the system unusable.

.sp
.LP
The following is an example of a \fBts_dptbl.c\fR file used for building the
new \fBts_dptbl\fR.

.sp
.in +2
.nf
/* BEGIN ts_dptbl.c */
#include <sys/proc.h>
#include <sys/priocntl.h>
#include <sys/class.h>
#include <sys/disp.h>
#include <sys/ts.h>
#include <sys/rtpriocntl.h>
/*
 * This is the loadable module wrapper.
 */
#include <sys/modctl.h>
extern struct mod_ops mod_miscops;
/*
 * Module linkage information for the kernel.
 */
static struct modlmisc modlmisc = {
	&mod_miscops, "Time sharing 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));
}
/*
 * array of global priorities used by ts procs sleeping or
 * running in kernel mode after sleep. Must have at least
 * 40 values.
 */
pri_t config_ts_kmdpris[] = {
         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,
};
tsdpent_t	config_ts_dptbl[] = {

/*  glbpri  qntm  tqexp  slprt  mxwt  lwt  */

    0,      100,  0,     10,    5,    10,
    1,      100,  0,     11,    5,    11,
    2,      100,  1,     12,    5,    12,
    3,      100,  1,     13,    5,    13,
    4,      100,  2,     14,    5,    14
    5,      100,  2,     15,    5,    15,
    6,      100,  3,     16,    5,    16,
    7,      100,  3,     17,    5,    17,
    8,      100,  4,     18,    5,    18,
    9,      100,  4,     19,    5,    19,
    10,     80,   5,     20,    5,    20,
    11,     80,   5,     21,    5,    21,
    12,     80,   6,     22,    5,    22,
    13,     80,   6,     23,    5,    23,
    14,     80,   7,     24,    5,    24,
    15,     80,   7,     25,    5,    25,
    16,     80,   8,     26,    5,    26,
    17,     80,   8,     27,    5,    27,
    18,     80,   9,     28,    5,    28,
    19,     80,   9,     29,    5,    29,
    20,     60,   10,    30,    5,    30,
    21,     60,   11,    31,    5,    31,
    22,     60,   12,    32,    5,    33,
    24,     60,   14,    34,    5,    34,
    25,     60,   15,    35,    5,    35,
    26,     60,   16,    36,    5,    36,
    27,     60,   17,    37,    5,    37,
    28,     60,   18,    38,    5,    38,
    29,     60,   19,    39,    5,    39,
    30,     40,   20,    40,    5,    40,
    31,     40,   21,    41,    5,    41,
    32,     40,   22,    42,    5,    42,
    33,     40,   23,    43,    5,    43,
    34,     40,   24,    44,    5,    44,
    35,     40,   25,    45,    5,    45,
    36,     40,   26,    46,    5,    46,
    37,     40,   27,    47,    5,    47,
    38,     40,   28,    48,    5,    48,
    39,     40,   29,    49,    5,    49,
    40,     20,   30,    50,    5,    50,
    41,     20,   31,    50,    5,    50,
    42,     20,   32,    51,    5,    51,
    43,     20,   33,    51,    5,    51,
    44,     20,   34,    52,    5,    52,
    45,     20,   35,    52,    5,    52,
    46,     20,   36,    53,    5,    53,
    47,     20    37,    53,    5,    53,
    48,     20,   38,    54,    5,    54,
    49,     20,   39,    54,    5,    54,
    50,     10,   40,    55,    5,    55,
    51,     10,   41,    55,    5,    55,
    52,     10,   42,    56,    5,    56,
    53,     10,   43,    56,    5,    56,
    54,     10,   44,    57,    5,    57,
    55,     10,   45,    57,    5,    57,
    56,     10,   46,    58,    5,    58,
    57,     10,   47,    58,    5,    58,
    58,     10,   48,    59,    5,    59,
    59,     10,   49,    59,    5,    59,

};

short config_ts_maxumdpri = sizeof (config_ts_dptbl)/16 - 1;
/*
 * Return the address of config_ts_dptbl
 */
tsdpent_t *
ts_getdptbl()
{
      return (config_ts_dptbl);
}

/*
 * Return the address of config_ts_kmdpris
 */
 int *
 ts_getkmdpris()
{
      return (config_ts_kmdpris);
}

/*
 * Return the address of ts_maxumdpri
 */
short
ts_getmaxumdpri()
{
       return (config_ts_maxumdpri);
}

/* END ts_dptbl.c */
.fi
.in -2

.SH SEE ALSO
.sp
.LP
\fBpriocntl\fR(1), \fBdispadmin\fR(1M), \fBpriocntl\fR(2), \fBsystem\fR(4)
.sp
.LP
\fISystem Administration Guide: Basic Administration\fR
.sp
.LP
\fIProgramming Interfaces Guide\fR
.SH NOTES
.sp
.LP
\fBdispadmin\fR does some limited sanity checking on the values supplied in the
configuration file. The sanity checking is intended to ensure that the new
\fBts_dptbl\fR values do not cause the system to panic. The sanity checking
does not attempt to analyze the effect that the new values will have on the
performance of the system. Unusual \fBts_dptbl\fR configurations may have a
dramatic negative impact on the performance of the system.
.sp
.LP
No sanity checking is done on the \fBts_dptbl\fR values specified in the
\fBTS_DPTBL\fR loadable module. Specifying an inconsistent or nonsensical
\fBts_dptbl\fR configuration through the \fBTS_DPTBL\fR loadable module could
cause serious performance problems and/or cause the system to panic.