| Chuck Stevens 2005-07-25, 10:01 pm |
| Based on information that seems to be between the lines in this thread, the
concept of "module" seems to include both instruction information and data
information, treated as a logical unit which as a whole is either in memory
or it is not. That's a particular implementation approach, but it is not
an approach that applies to all environments. In our environment, "virtual
memory swaps" take place *only* for data; there is never a need to write
object code back out to disk; and there's a whole suite of mechanisms that
fine-tune how sticky a particular piece of (code or data) information needs
to be and how readily its space can be reused for something else. Code
gets read in if it's not there when somebody goes to it or performs it; it
gets marked absent if the system decides it needs the space; but it never
gets written back out. Thus, the concept of binding code to data in some
way may be a really useful and productive concept in designing an
application, but it doesn't necessarily require that the underlying hardware
platform actually act that way.
(no more below)
-Chuck Stevens
"Howard Brazee" <howard@brazee.net> wrote in message
news:dbogo5$k74$1@peabody.colorado.edu...
>
> On 21-Jul-2005, "Chuck Stevens" <charles.stevens@unisys.com> wrote:
>
by[color=darkred]
will[color=darkred]
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>
> Sometimes compilers for supercomputers actually take code and make
multiple
> copies - which are executed simultaneously.
>
> But those computers are designed to avoid virtual memory swaps as much as
> possible.
>
>
never[color=darkred]
>
> VM machines have various degrees of smarts and successes. The easiest
thing to
> do is to swap a whole program out when memory is needed by another
program.
> But if it has control over various modules, it can be smarter about just
> swapping out enough modules to free up the required amount of memory.
On the
> other hand - if it picks the small modules to swap out - programs with
small
> modules will be the ones that are slowed down when this happens.
|