Reducing VMS Ada .exe sizes... How?

Reducing VMS Ada .exe sizes... How?

[Fred Stluka]

VAX Ada or VMS Linker gurus,

Is there a way to build an executable image which contains
the code for *part* of an Ada package?

If I "with" an Ada package, but only call one of its routines,
is there any way to avoid having the code for all the routines
in the package (and everything they reference) linked into the
executable?

Please mail; I will summarize,
--Fred
-- 

Fred Stluka                              Internet: stluka@software.org
Software Productivity Consortium         UUNET:    ...!uunet!software!stluka
2214 Rock Hill Rd, Herndon VA 22070 USA 

Re: Reducing VMS Ada .exe sizes... How?

[PHALL]

you don't really say what the exact problem is, however if the problem
is that the image size is very large then check the linker map to see
how many modules are being linked. if this value is approx 96 it is likley
that the linker has stopped performing demand zero compression.
the linker option ISD_MAX specifies the maximum number of image sections
allowed in an image. The default is approz 96. If the total number of
image sections reaches or exceeds this value, demand zero compression stops.

Re: Reducing VMS Ada .exe sizes... How?

[Fred Stluka]

In article <91134.084320PHALL@ESOC.BITNET> PHALL@ESOC.BITNET writes:
> you don't really say what the exact problem is, however if the problem
> is that the image size is very large ...

Yes, the problem is that the image size is huge (7500 blocks),
wasting space on disk and time at image activation.

I suspect that a major contributing factor is that lots of 
stuff which is in packages I reference but which I don't ever
use is being included in the image.  I suspect that the linker 
always links in an entire object module, regardless of how
much is needed to resolve all references.  Thus an Ada package
containing many routines, or a C file containing many functions,
is always completely included in the image, even when many of 
the routines are never called.  Once these rouitnes are included,
then other routines which they reference (but which I also never
call from my code) must also be included, and so on.

Therefore, my question to the net was how to prevent these routines
from being linked into the image.  I am still interested in an 
answer to that question, but other tips like the one below are 
also appreciated.

> ... then check the linker map to see
> how many modules are being linked. if this value is approx 96 it is likley
> that the linker has stopped performing demand zero compression.
> the linker option ISD_MAX specifies the maximum number of image sections
> allowed in an image. The default is approz 96. If the total number of
> image sections reaches or exceeds this value, demand zero compression stops.

What is demand zero compression?  Are you saying that pages which
are entirely zero-filled are stored that way on disk in the image 
instead of being generated dynamically during a page fault, if the
image has more than 96 or so sections?

--Fred
-- 

Fred Stluka                              Internet: stluka@software.org
Software Productivity Consortium         UUNET:    ...!uunet!software!stluka
2214 Rock Hill Rd, Herndon VA 22070 USA 

Re: Reducing VMS Ada .exe sizes... How?

[Fred Stluka]

In article <91134.084320PHALL@ESOC.BITNET> PHALL@ESOC.BITNET writes:
> you don't really say what the exact problem is, however if the problem
> is that the image size is very large then check the linker map to see
> how many modules are being linked. if this value is approx 96 it is likley
           ^^^^^^^
> that the linker has stopped performing demand zero compression.
> the linker option ISD_MAX specifies the maximum number of image sections
                                                            ^^^^^^^^^^^^^^
> allowed in an image. The default is approz 96. If the total number of
> image sections reaches or exceeds this value, demand zero compression stops.
  ^^^^^^^^^^^^^^

Which is the relevant number: "image sections" or modules"?  From the
"Image Synopsis" of my link map:

     Number of files:              960
     Number of modules:           1039
     Number of program sections:   156
     Number of image sections:      72

--Fred

-- 

Fred Stluka                              Internet: stluka@software.org
Software Productivity Consortium         UUNET:    ...!uunet!software!stluka
2214 Rock Hill Rd, Herndon VA 22070 USA 

Re: Reducing VMS Ada .exe sizes... How?

[PHALL]

Check the number of image sections in the image synopsis.
If this value is approx 96, it could be that the linker has stopped
performing demand zero compression.

Demand zero compression is the extracting of contiguous, uninialized
writable pages from an image section and placing these pages into a
newly created demand zero section. A demand zero image section contains
uninitialized, writeable pages which do not occupy physical memory
in the image file on disk, but which when accessed during program execution
are allocated memory and initialized to zero  by VMS.

Re: Reducing VMS Ada .exe sizes... How?

[Osman]

Maybe I've missed the point but have you considered compiling some of the 
modules into a shareable image (or using them as a shareable image). This has
the advantage that if you use them in several sets of programs you still only need one file.

Sorry if I've missed the point.

Cabbage.  

Re: Reducing VMS Ada .exe sizes... How?

[Fred Stluka]

In article <965@hwee.UUCP> osman@hwee (Osman) writes:
> Maybe I've missed the point but have you considered compiling some of the 
> modules into a shareable image (or using them as a shareable image). This has
> the advantage that if you use them in several sets of programs you still only 
> need one file.

Doesn't help (I think).

I am only building one program.  It "with"s a large Ada 
package containing hundreds of routines (Ada bindings to
a non-Ada collection of routines).  I only call a couple
of the routines, but the entire package, and therefore
all of the non-Ada routines also, get linked into the 
executable image.

Any way to avoid this large image size, short of breaking
up the Ada bindings package into multiple packages?  Would
subunits help?

I think the problem would go away if I could convert the 
single Ada bindings package into an object module library,
or shareable image, with one object per routine.  Then I 
could get the linker to selectively link in individual 
Ada bindings routines.  I'd rather not have to modify the
source too much to do this though.

--Fred
-- 

Fred Stluka                              Internet: stluka@software.org
Software Productivity Consortium         UUNET:    ...!uunet!software!stluka
2214 Rock Hill Rd, Herndon VA 22070 USA 

Re: Reducing VMS Ada .exe sizes... How?

[Orville R. Weyrich]

In article <1991May22.133537.419@software.org> stluka@software.org (Fred Stluka) writes:
>I am only building one program.  It "with"s a large Ada 
>package containing hundreds of routines (Ada bindings to
>a non-Ada collection of routines).  I only call a couple
>of the routines, but the entire package, and therefore
>all of the non-Ada routines also, get linked into the 
>executable image.
>
>Any way to avoid this large image size, short of breaking
>up the Ada bindings package into multiple packages?  Would
>subunits help?

This may not help your situation much, but the problem is with the dumb linker
that you seem to have in your environment. Some Ada systems are able to figure
out which entry-points are never used and to not include them in the run-time
image. (The professional version of Meridian Ada and/or Janus Ada come to mind,
but you'd best check with the vendors for reliable information). The Turbo
Pascal compiler also does this (proof of concept, for whatever that is worth).



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