🚀 go-pugleaf

>From article <1991May22.210541.1@vax1.tcd.ie>, by mtynan@vax1.tcd.ie:
>> 
>> I've heard rumours that the compile-link cycle time is greatly reduced
>> when running Borland C++ in protected mode, is this true?

The big bottleneck that leads to complaints about long build times is
the time it takes to link a Windows app using the real mode linker
under Windows in enhanced mode.  Here's why and what to do about it:

The real mode linker will use EMS and disk as available for
swapping data (and XMS with the right switches, but it isn't really
relevant to this discussion, so  I'll simplify by ignoring it).
Swapping to EMS is a lot faster than swapping to disk. If you run the
linker under DOS it will by default use any EMS that is available.

The difference in speed between swapping to EMS and to disk by the
linker happens to be accentuated in a specific combination of
circumstances that occurs when linking the standard libraries that are
used for Windows apps. It has to do with the number of symbols and the
pattern of references to them in the Windows import library and the
RTL. This means that linking a Windows app using the real mode linker
may be very slow if swapping is to disk, but acceptibly fast if
swapping is to EMS.

When running BC++ under Windows, the task will only have EMS available
if you use a PIF that allocates some EMS. If you run without a PIF,
the linker will not have EMS, will have to swap to disk and will
likely be very slow at linking a Windows app.

Even if you specify EMS in the PIF, Windows in enhanced mode has an
additional gotcha: Windows simulates memory (low, EMS and XMS) by
swapping to disk. So the PIF can specify EMS, the linker can think
that it is swapping to EMS, but Windows can actually be swapping to
disk. This extra layer of emulation makes the link even slower than
having the linker swap directly to disk.

To make sure that Windows uses real EMS memory, specify in the PIF
that the EMS memory is locked. If you do that, Windows will not let
you run the task unless the amount of EMS requested is really
available. You should not have to request more than 1.5Mb for maximum
performance.

That will get you maximum speed from the real mode linker under
Windows. However the protected mode linker, which needs to do no
swapping at all, will still be faster. Typical times that I have seen
on a small app were: 30 seconds using real mode linker under DOS, 40
sec under enhanced mode Windows with EMS locked, 10 minutes with EMS
not locked, and 7 seconds using BCX under standard mode Windows.

Another little known fact is that BCCX spawns the real mode linker,
not the protected mode one. To use the protected mode linker you need
to build using BCX (the protected mode IDE) or explicitly call TLINKX
if you are using the command line tools.

 -- sidney markowitz <sidney@borland.com>
    Borland International (Languages - R&D)