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Re: Emacs 32 -> 64 bits on Win32


From: Fabrice Popineau
Subject: Re: Emacs 32 -> 64 bits on Win32
Date: Sun, 20 Nov 2011 23:16:48 +0100

I'm quite sure it is, but I don't have a 64-bit MinGW development
environment installed to verify that.  I suggest to ask a question on
address@hidden.

I installed it and I can confirm it is the same size for int and long.
 
> Although, Emacs tries to virtually allocate a 2Gb heap. What should be done
> on a 64bits machine ?
> For sure, the heap could grow much further.

How much physical memory would a typical 64-bit Windows box have?  I'd
say set the reserved heap size to twice that much.  If the page file
size is something like 1.5 to 2 times the size of physical RAM,
Windows will probably refuse a larger reservation anyway.

No it doesn't.
Well, it was rather the process I find questionable when switching to a large address space : 
start trying to reserve 2Gb (hard coded value) and diminish the size up to the point where it will fit.

With a 64 bits address space, you can reserve much more, even if after that, you aren't able
to commit the pages. I have a 4Gb machine and I have been able to reserve about
540Gb. So the question is : with a 64 bits emacs, where do you start ? 
The 2Gb limit was half the address space for 32bits, and it makes sense to start there.
But with 64bits, the 2Gb are honoured easily and you can even claim for more.
So where do you start ?

I found this which may be of interest :
http://msdn.microsoft.com/en-us/library/aa384271(v=VS.85).aspx
if we prefer to stick with "small" address space.

Fabrice



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