GCC and Memory Organization

GCC and Memory Organization

[William N. Zanatta]

Hello brothers,

   I have a question on memory organization...
   In my Computer Architeture classes, I've learned something like that 
there are two ways to organize data in memory.
   The first one puts it in a linear mode like:

      +---------------+
12k  | z | z |   |   |
      |---------------|
8k   | y | y | z | z |
      |---------------|
4k   | x | x | x | y |
      +---------------+

   And the second way is a non-linear, a block mode like:

      +---------------+
12k  | z | z | z | z |
      |---------------|
8k   | y | y | y |   |
      |---------------|
4k   | x | x |   |   |
      +---------------+

   The second way should be faster than the first one for memory 
management, right?! That a kindda obviuos as it wouldn't be necessary to 
scan all the block to find the next entry. Also it can be expensive 
since the 4k block is allocated for only 2k of real data.

   My question is, how does GCC works with this? Does it have any switch 
for optimizing (or not) the code?? What's the default action???

   Thank you, keep it hard!

William Zanatta

Re: GCC and Memory Organization

[Glynn Clements]

William N. Zanatta wrote:

>    I have a question on memory organization...
>    In my Computer Architeture classes, I've learned something like that 
> there are two ways to organize data in memory.
>    The first one puts it in a linear mode like:
> 
>       +---------------+
> 12k  | z | z |   |   |
>       |---------------|
> 8k   | y | y | z | z |
>       |---------------|
> 4k   | x | x | x | y |
>       +---------------+
> 
>    And the second way is a non-linear, a block mode like:
> 
>       +---------------+
> 12k  | z | z | z | z |
>       |---------------|
> 8k   | y | y | y |   |
>       |---------------|
> 4k   | x | x |   |   |
>       +---------------+
> 
>    The second way should be faster than the first one for memory 
> management, right?! That a kindda obviuos as it wouldn't be necessary to 
> scan all the block to find the next entry. Also it can be expensive 
> since the 4k block is allocated for only 2k of real data.
> 
>    My question is, how does GCC works with this? Does it have any switch 
> for optimizing (or not) the code?? What's the default action???

This isn't a compiler issue. The different layouts would require
different source code. The former corresponds to a one-dimensional
array, while the latter corresponds to a two-dimensional array.

-- 
Glynn Clements <glynn.clements@virgin.net>

Re: GCC and Memory Organization

[William N. Zanatta]

Glynn Clements wrote:

> This isn't a compiler issue. The different layouts would require
> different source code. The former corresponds to a one-dimensional
> array, while the latter corresponds to a two-dimensional array.
> 

Do you know any document on the web where I can study more about this issue?


William

Re: GCC and Memory Organization

[William N. Zanatta]

> 
> This isn't a compiler issue. The different layouts would require
> different source code. The former corresponds to a one-dimensional
> array, while the latter corresponds to a two-dimensional array.
> 

I guess I found something. Looks like I'm talking about the concepts of 
segmentation and paging. Is that right?
In the following site there's a interesting map for understanding the 
concepts of VM.

http://cne.gmu.edu/modules/vm/index.html

Thank you again,

William

Re: GCC and Memory Organization

[Glynn Clements]

William N. Zanatta wrote:

> > This isn't a compiler issue. The different layouts would require
> > different source code. The former corresponds to a one-dimensional
> > array, while the latter corresponds to a two-dimensional array.
> > 
> 
> I guess I found something. Looks like I'm talking about the concepts of 
> segmentation and paging. Is that right?

Maybe, but segmentation and paging are only really relevant if you're
designing a CPU or an OS kernel. A program just sees a flat address
space.

-- 
Glynn Clements <glynn.clements@virgin.net>