09-13-2015
After many hours of travel, and some sleep I have for you - this link with the basis information:
https://www-01.ibm.com/support/knowl...rg_support.htm
Basically, what happens is that system and code remain in segments 0 and 1.
When maxdata is not equal to 0 (zero) - which is default, segment 2 is used for the stack and application .data (pre-initialized data) and .bss (aka heap for malloc calls) start in segment 3 and continue for the number of segments specified.
As you mentioned in your initial question the "official" large memory support model has a maximum MAXDATA value of 0x80000000 - so that is 2.25 G total (256MB (roughly) for the stack, and 2 GByte (8x 256 MByte) for application .data and .bss
From the discussion, I do not think you will want to use the
DSA - dynamic segment allocation - option (so-called
or the VERY large memory option). However, if 2G Byte for .data and .bss is not going to be enough you may need to use that.
Back to "shared" memory - the default memory model setup uses only segments 0, 1, and 2 for the memory model - the segments there are 12 segments (numbers 3-12 and 14 are used by shmap or mmap routines). Historically, segments 13 and 15 were used by global shared libraries text and data. When you use the DSA option global shared libraries are not used - instead the shared libraries are loaded "privately" into segment 15 - both text and data. This free up segment 13 giving an application at least one additional segment.
If you are not using shmap or mmap routines then the "very large" model should work fairly easy. However, if you do use either of these routines they may impact the maximum memory available via malloc(). - keyword here:
potential impact!
I hope this answers your question well enough.
Michael
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LEARN ABOUT OPENSOLARIS
size
size(1) User Commands size(1)
NAME
size - print section sizes in bytes of object files
SYNOPSIS
size [-f] [-F] [-n] [-o] [-V] [-x] filename...
DESCRIPTION
The size command produces segment or section size information in bytes for each loaded section in ELF object files. size prints out the
size of the text, data, and bss (uninitialized data) segments (or sections) and their total.
size processes ELF object files entered on the command line. If an archive file is input to the size command, the information for each
object file in the archive is displayed.
When calculating segment information, the size command prints out the total file size of the non-writable segments, the total file size of
the writable segments, and the total memory size of the writable segments minus the total file size of the writable segments.
If it cannot calculate segment information, size calculates section information. When calculating section information, it prints out the
total size of sections that are allocatable, non-writable, and not NOBITS, the total size of the sections that are allocatable, writable,
and not NOBITS, and the total size of the writable sections of type NOBITS. NOBITS sections do not actually take up space in the filename.
If size cannot calculate either segment or section information, it prints an error message and stops processing the file.
OPTIONS
The following options are supported:
-f Prints out the size of each allocatable section, the name of the section, and the total of the section sizes. If there is no section
data, size prints out an error message and stops processing the file.
-F Prints out the size of each loadable segment, the permission flags of the segment, then the total of the loadable segment sizes. If
there is no segment data, size prints an error message and stops processing the file.
-n Prints out non-loadable segment or non-allocatable section sizes. If segment data exists, size prints out the memory size of each
loadable segment or file size of each non-loadable segment, the permission flags, and the total size of the segments. If there is no
segment data, size prints out, for each allocatable and non-allocatable section, the memory size, the section name, and the total
size of the sections. If there is no segment or section data, size prints an error message and stops processing.
-o Prints numbers in octal, not decimal.
-V Prints the version information for the size command on the standard error output.
-x Prints numbers in hexadecimal, not decimal.
EXAMPLES
The examples below are typical size output.
Example 1 Producing size information
example% size filename
2724 + 88 + 0 = 2812
Example 2 Producing allocatable section size information
example% size -f filename
26(.text) + 5(.init) + 5(.fini) = 36
Example 3 Producing loadable segment size information
example% size -F filename
2724(r-x) + 88(rwx) + 0(rwx) = 2812 ... (If statically linked)
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWbtool |
+-----------------------------+-----------------------------+
SEE ALSO
as(1), cc(1B), ld(1), ar.h(3HEAD), a.out(4), attributes(5)
NOTES
Since the size of bss sections is not known until link-edit time, the size command will not give the true total size of pre-linked objects.
SunOS 5.11 16 Oct 1996 size(1)