Soem questions additionals.

QNX Newsgroups (Archives) comp.os.qnx
1

Hello Friends, here again with some “simple” questions in 2 idioms… thanks
a lot…


1.- QNX trabaja con particiones fijas o variables ?

2.- Existen las siguientes estrategias de administracion de la memoria real:
First-Fit.- Ubica un proceso en el primer espacio libre (hueco).
Best-Fit.- Ordena ascendentemente los espacio libres y ubica el proceso
en el primero que lo pueda contener.
Worst-Fit.- Ordena descendentemente los espacio libres y ubica el
proceso en el primero que lo pueda contener.
Que estrategia aplica QNX ?

3.- Si existen espacio libres (huecos) colindantes en la memoria, estos son
unidos por el S.O ? Si o No?

4.- Que tecnica utiliza para manejar la memoria virtual QNX ?

5.- QNX utiliza paginación ?
6.- Cuanto ocupa cada página ?
7.- Cual es el minimo de memoria requerida para trabajar con QNX ?

1.- QNX works with fixed or partitions variables, how ?
2.- There are the following strategics of real memory management:
First-Fit.- To position a process in the first free space.
Best-Fit.- To put in ascending order the free spaces and to position a
process in the first free space.
Worst-Fit.- To put in descending order the free spaces and to position a
process in the first free space.
What strategic is used for QNX ?

3- If exists adjacents free spaces, are these joins for QNX ?
4.- What technique is used QNX for to manage the virtual memory ?
5.- Is The Pagination technique used for QNX ?
6.- How is occupy or store each page ?
7.- What is the minimum measure of memory required to work with QNX ?




Javier Melendez
Renzo Cruz

2

Javier Melendez <javier@barreda.com.pe> wrote:

Hello Friends, here again with some “simple” questions in 2 idioms… thanks
a lot…

I’ll take a shot at them.

I’ll assume you’re talking about QNX 6.

1.- QNX works with fixed or partitions variables, how ?

Fixed sized hard drive partitions. They can not be resized after being
created.

2.- There are the following strategics of real memory management:
First-Fit.- To position a process in the first free space.
Best-Fit.- To put in ascending order the free spaces and to position a
process in the first free space.
Worst-Fit.- To put in descending order the free spaces and to position a
process in the first free space.
What strategic is used for QNX ?

QNX uses a virtual address system for process, through the MMU. This
means that scattered pages of physical memory can be “coalesced” into
virtually contiguous pages of process memory when that memory is given
to processes.

This makes the use/layout of physical memory less important.

I’m not sure the details of how QNX hands out physical memory – I think it
tends to be sort of first-fit, but none of the above really applies since
a request can be satisfied by multiple dis-continguous pieces.

If a piece is explicitly allocated to be physically contiguous in processor
address space (e.g. for DMA safe memory), the above issues would apply, but
this is NOT the usual case for getting memory for a process.

Memory is handed out by the os a “page” at a time – in all current
implementations, the page size is 4k.

Internal to a process, the memory is broken into potentially smaller
chunks by the malloc() library – how this is done depends on the
particular library implementation, and can be over-ridden. It is not
an OS issue.

3- If exists adjacents free spaces, are these joins for QNX ?

Yes, but not particularly important, as non-adjacents free spaces can
also be virtually “joined” for delivery to a process.

4.- What technique is used QNX for to manage the virtual memory ?

Full MMU enabled, every process has its own full virtual address space.
Exact technique/implementation detail depends on the platform.

Neither page nor swap to disk is supported.

5.- Is The Pagination technique used for QNX ?

No.

6.- How is occupy or store each page ?

Not done.

7.- What is the minimum measure of memory required to work with QNX ?

Depends on what you want to do – a minimal system running XIP from ROM
would require extraordinarily less RAM than a desktop development system
or a high-end packet switch.

-David

QNX Training Services
I do not answer technical questions by email.