Re: Fastcode MM memory usage

> > It's very difficult to measure the memory usage using task manager. The
> > usage numbers given by the B&V replay tool is the actual address space used
> > by the process and is IMO the best measure.
>
> I'm having trouble following here. The memory usage reported in perfmon
> and the task manager is what's actually allocated, right?

For PerfMon it depends entirely on what you've chosen to monitor. There
is a *long* list of values. The column "Mem Usage" in Task Manager is
called "Working Set" in PerfMon.

Working Set is roughly the amount of RAM currently in use by the
process. For a computer that has plenty of free RAM, this value is
typically very stable. For a computer that does not have enough free
RAM, this value will be constantly changing as pages are first swapped
through the disk cache and then through the hard drive.

In addition, certain events (like minimizing the application) cause the
operating system to "trim the working set". Basically, the operating
system tosses memory pages that haven't been touched in a while.


> So it's a
> different value than that reported by the B&V, but it seems like it
> would be just as valid.

You have a point. Smaller working set = good thing. A memory manager
that produces a smaller working set, either by design or by luck, places
a smaller burden on the operating system.


> We don't really have a lot of trouble with
> fragmentation and address space creep, so I'm more concerned about
> limiting the overall system impact by keeping as little memory allocated
> as possible when we aren't using it. It seems like I'd want to use the
> numbers from the task manager in that case, wouldn't I?

That makes sense. Just bare in mind that the number is ephemeral. Even
the tiniest change (like showing a dialog box) can dramatically affect
the working set.


- Brian
.

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