Data Structure Sizing Rules - Sun Microsystems Sun Workstation 100U System Manager's Manual

Building Sun Workstation Kernels Sample Configuration Files
Appendix D. Data Structure Sizing Rules
Certain kernel data structures are sized at compile time according to the maximum number of
simultaneous users expected, while others are calculated at boot time based on the physical
resources present; e.g. memory. This appendix lists both sets of rules and also includes some
hints on changing built-in limitations on certain data structures.
D.I. Compile Time Rules
The file
'Y'/
conl/ param.c contains the definitions of almost all data structures sized at compile
time. This file is copied into the directory of each configured kernel to allow configuration-
dependent rules and values to be maintained. The rules implied by its contents are summarized
below (here MAXUSERS refers to the value defined in
th~
configuration file in the "maxusers"
rule).
nproc
The maximum number of processes which may be running at any time. It is defined to be
20
+
8
*
MAXUSERS and referred to in other calculations as NPROC.
ntext
The maximum number of active shared text segments. Defined as
24
+
MAXUSERS.
ninode
The maximum number of files in the file system which may be active at any time. This
includes files in use by users, as well as directory files being read or written by the system
and files associated with bound sockets in the UNIX ipc domain. This is defined as
(NPROC
+
16
+
MAXUSERS)
+
32.
nfUe
The number of "file table" structures. One file table structure is used for each open,
unshared, file descriptor. Multiple file descriptors may reference a single file table entry
w hen they are created through a dup call, or as the result of a fork. This is defined to be
16
*
(NPROC
+
16
+
MAXUSERS) / 10
+
32
ncallout
The number of "callout" structures. One callout structure is used per internal system event
handled with a timeout. Timeouts are used for terminal delays, watchdog routines in device
drivers, protocol timeout processing, etc. This is defined as 16
+
NPROC.
nclist
The number of "c-list" structures. C-list structures are used in terminal i/o. This
IS
defined as 100
+
16
*
MAXUSERS.
nmbclusters
The maximum number of pages which may be allocated by the network. This is defined as
256 (a quarter megabyte of memory) in /sys/h/mbuf.h. In practice, the network rarely uses
this much memory. It starts off by allocating 64 kilobytes of memory, then requesting more
as required. This value represents an upper bound.
nquota
The number of "quota" structures allocated. Quota structures are present only when disc
quotas are configured in the system. One quota structure is kept per user. This is defined
to be (MAXUSERS
*
9) / 7
+
3.
7 January
1984
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