Re: Big allocation AND per process memory!

Tech-Archive recommends: Repair Windows Errors & Optimize Windows Performance

I'm not sure what is your question.

First, let's confine ourselves to the usual 2GB kernel space/2GB user space
setup.

Next, an allocation is in kernel space or user space. An allocation will not
span. That's just the way the OS is (I won't go into reasons).

Next, in the kernel 2GB some space is taken with executables (binaries like
the kernel, HAL, drivers), page tables, lookasides of various kinds and
plain old data.

Next, in the kernel an allocation will be satisfied only from a kind of
storage such as pageable or non-paged (there are also flavors that are
suitable for DMA, etc, etc.). These types are confined to virtual memory
ranges.

Next, some other virtual ranges just aren't used.

The end result is that a given allocation, in a freshly booted system
(nobody has grabbed memory beyond what the OS and device drivers must have),
the maximum allocation is going to be rather less than 2GB.

The short of all this is that memory comes in lots of flavors, and an
allocation always includes a flavor (maybe by default), and a flavor can be
carved out of only a certain virtual range, a range that is always less than
the 2GB that comprises all possible flavors.

Similar reasoning applies to user space.

--
James Antognini
Windows DDK and WDK Support


This posting is provided "AS IS" with no warranties, and confers no rights.



"Ali" <abdulrazaq@xxxxxxxxx> wrote in message
news:1129306145.199816.305290@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Thanks Born,
>
> 1. Boot your system with /3GB (Windows NT & 2000) or /4GT (Windows
> 2003) switch. This way, kernel will only use 1 GB and applications can
> use 3 GB.
>
> 2. If you have more physical memory installed and your hardware is
> Intel with PAE support, boot Windows with /PAE switch. This way you can
> use up to 64 GB memory from your application via AWE (Address Windowing
> Extensions).
>
> See this link for details.
>
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/memory/base/large_memory_support.asp
>
>
> I believe that this is for allocating space for a file not for a
> process itself! right? nothing math just few thoughts;-)
>
> Thanks for post.
> Regars
> -ali
>


.

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