Re: Kernel malloc/realloc?

From: David J. Craig (SeniorDriversWriter_at_shogunyoshimuni.com.net)
Date: 02/15/04 

Date: Sat, 14 Feb 2004 22:36:09 -0500

No, stupid is calling functions belonging to Win32, 'SYSTEM'. Windows
NT has a kernel that has several possible environments above it and one
of them is Win32. There is or was a POSIX environment. They also had a
OS/2 environment at one time because the OS/2 Brief would run under NT4.
The use of the GlobalAlloc function is not even recommended since the
overhead is high. So how does a function in kernel32.dll even belong in
the 'Development Device Drivers' newsgroup? The first question was
about allocating and reallocating memory under Windows 2000+.

"Alex" <AlX@a> wrote in message
news:Oi8rNa28DHA.488@TK2MSFTNGP12.phx.gbl...
> Do you even know the diffrence between a RTL function and a System API
> function?
>
> As it's been sed before, pointing to RTL source code to understand how
> **SYSTEM** APIs work is stupid.
>
> Sorry, if it's ofensive, but this is what it is
>
> MSDN Library April 2003:
> GlobalAlloc:
> GMEM_MOVEABLE:
> "Allocates movable memory. Memory blocks are never moved in physical
memory,
> but they can be moved within the default heap."
>
> **"never moved in physical memory"**
>
>
> "Tim Roberts" <timr@probo.com> wrote in message
> news:9c9r20dgm2d1drglccnmf30g73lj87r2u4@4ax.com...
> > "Alex" <AlX@a> wrote:
> > >
> > >"Tim Roberts" <timr@probo.com> wrote:
> > >
> > >> "Alex" <AlX@a> wrote:
> > >> >
> > >> >"Tim Roberts" <timr@probo.com> wrote:
> > >> >
> > >> >Isn't the same allgorithm behing the user mode reallocation (not
> > >necesarly
> > >> >realloc, i'm shure this thread has nothing to do with the
acctual
> realloc
> > >> >function :P) which we all use in user mode apps?
> > >>
> > >> No. Both relloc in the C run-time library and
> LocalRealloc/GlobalRealloc
> > >> use the new/copy/free model.
> > >
> > >Is that a fact? Or a beleif?
> >
> > The source code for Microsoft's C run-time library is included with
Visual
> > C++. You can look it up. If there's empty space following the
block, it
> > just expands the block. Otherwise, it's new/copy/free.
> >
> > Think about it for a bit. Your page table magic will ONLY work if
all
> heap
> > allocations are done in units of whole pages. As soon as you have
two
> > objects in the same page, you can't alter the mapping without
screwing up
> > the other objects in the page. The C run-time malloc and the Win32
heap
> > alloc work in units of 32 bytes.
> >
> > >> in order to save page space. So, 80000000 has the DOS interrupt
> vectors
> > >> from physical address 0, 800C0000 has the VGA BIOS at physical
address
> > >> C0000, and so on.
> > >
> > >This mapping is documented behaviour? For what OS-es is it used?
> >
> > I've never seen it documented by Microsoft, but it's fact, and
operating
> > system routines rely on it. I know it's true for the NT-based
systems
> > (NT/2K/XP). It used to be true on Windows 3.1. I do not remember
about
> > 95/98.
> > --
> > - Tim Roberts, timr@probo.com
> > Providenza & Boekelheide, Inc
>
>

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