I would normally agree. However this is a *specific* case where it
would be quite nice to do this. In this *specific* case, there is no
64-bit option for me nor is worrying about the VM an option either.
The amount of memory is pretty small anyway both ways (allocation and
available).
Let me put it another way. I'd like to learn how to do this in OS X
notwithstanding all the exceptionally valid points you've made. I
understand its possible that I can't do this due to permissions or
other reasons. But if I can, it would be nice. If I can't, I'd just
like to know.
One fun thing to do with this is to simply do an Instrument's like log
file showing free physical RAM of a machine over time.
On Aug 27, 2008, at 11:48 PM, Bill Bumgarner wrote:
On Aug 27, 2008, at 9:31 PM, Alex Kac wrote:
I need to check for free RAM before performing a specific
operation. I've Googled and checked in the docs and I suspect its
my terminology that's just out of whack.
So what is the best way to find out how much available RAM is
available in a Cocoa app?
That question isn't entirely relevant to coding on a multi-user,
multi-processing, VM'ing system.
It is also a question that will change rapidly due to circumstances
well beyond your application's control.
If you poke about the various mach_* APIs, you can grab some
relevant statistics such as paging event rate or some stats on
current memory usage, but it will largely just be hints.
In general, you should allocate what you need, use it as you see
fit, and then release it when done. You generally use malloc()
throughout, but vm_allocate() and friends can be used for more
specialized memory management needs.
The real questions is why do you think you need to know how much RAM
is available before doing something?
Are you looking for contiguous address space? You'll probably want
to go 64 bit, then, as 32 bit will have much less than 4GB of
contiguous address space available.
Are you looking to avoid paging? If so, you are kind of out of
luck. There is nothing that can prevent another app from deciding
to do something similar and forcing the system into paging death.
Something else?
b.bum
Alex Kac - President and Founder
Web Information Solutions, Inc.
"Forgiveness is not an occasional act: it is a permanent attitude."
-- Dr. Martin Luther King
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