Modifying tunable parameters

SCODB has a number of parameters whose value can be tuned to balance functionality and memory usage. These parameters are kept in the /etc/conf/pack.d/scodb/tune.h file; use the /bin/modtunes command to modify these parameters. modtunes verifies that the values supplied do not go out of valid ranges. As an example, to change the parameters interactively, type:

   $ cd /etc/conf/pack.d/scodb
   $ bin/modtunes -f tune.h
   	.
   	.
   	.
   display of the current values of the parameters
   prompts for new values

   $ cd /etc/conf/pack.d/scodb
   $ bin/modtunes -f tune.h HISTORY=40
   $

SCODB tunable parameters

Name	Purpose	Default value
LINETB	size of line table	1
TTY_OTHER	other tty definition	0
TTY_CONSOLE	console tty definition	1
TTY_WY60	WY60 tty definition	2
SYMTB	symbol table size	200000
STUNTB	structure table size	130000
VARTB	variables table size	55000
STACK	debugger stack size	8192
HISTORY	number of history lines remembered	32
VARS	number of debugger variables allowed	16
BKP	number of breakpoints	16
DECL	number of declaration slots	16
ALIAS	alias table size	8
SYSTTY	system tty	1
SSREG	dump registers during single-stepping	0
DBKEY	debugger entry key	24
MAINDB	1 to turn SCODB on; otherwise 0	0

The values of these parameters are numeric, except where otherwise noted in the following list. An optional K can be used at the end of the number to multiply the value by 1024.

LINETB

should be set to twice the number of lines of source code being recompiled with line numbers. If this value is too small, the next kernel relink will produce an error message similar to the following:

   db_linetable in unix would only fit 1 out of 2338 bytes
   

   Corrected table sizes in /etc/conf/pack.d/scodb/tune.h
   ready for next relink

The table size is then automatically corrected so that the next time you re-link the kernel the table will fit correctly. This automatic sizing sets the table size to the exact minimum size.

LINETB can be set to 1 to force automatic sizing of the line number table. This is useful when you want to keep the kernel size as small as possible.

SYMTB

must be large enough to fit all the kernel symbols. If its value is not sufficient, not all of the kernel symbols will be included in the debugger symbol table, which can make debugging difficult. The getsym command gives an exact size required for a given kernel loaded with SCODB; in this case, 71220 bytes:

   $ /etc/conf/pack.d/scodb/bin/getsym /unix
   $ ls -l symbols
   -rw-r--r--   1 root     root       71220 Jun  8 15:39 symbols

SYMTB should be given a value that is somewhat larger than reported by the getsym command, to allow for growth of the tables.

STUNTB

For proper usage, this must be as large as the stundef file (/etc/conf/pack.d/scodb/defs/stun.def); This parameter is automatically set to the proper size when the kernel is linked.

VARTB

must be as large as the varidef file (/etc/conf/pack.d/scodb/defs/vari.def). This parameter is automatically set to the proper size when the kernel is linked.

STACK

should not be set to a value below 6K.

SYSTTY

determines the display unit used by the kernel. By default, the value is 1, which specifies the built-in console. SCODB allows use of serial terminals as the system console, and has support for Wyse 60 terminals, which can be selected by setting the SYSTTY parameter to 2. To select a non-supported terminal, set the value to 0.

SSREG and MAINDB

The value can be numeric (zero or one), or true or false.

DBKEY

determines what key is configured to allow the user access to SCODB, and should be a key used infrequently in normal operation. The value can either be numeric or in the form 'x' (complete with quotation marks), denoting the character x. A control character may be represented as '^x'.