Memory management question

Memory management question

[Rodrigo Fernandez-Vizarra Bonet]

Hi,

I'm developing a linux module and I'm having some trouble with the
memory management in Linux.

Basically, what I want to do is to reserve some physical pages from the
kernel when I install the module (insmod module.o), and when a process
requests them (with mmap), I want to map that pages in the process
virtual memory area.

That's what I'm doing now.
1.- In the kernel I get some physical pages with get_free_page or with
__get_free_page.
2.- I create a device entry en /dev/ called pmm with
module_register_chrdev() with my own version of mmap.
3.- This mmap function uses the function remap_page_range() to map one
of the physical pages into the calling process virtual memory. Of course
the calling process must explicitly call mmap on the new device created
before.
4.- In the kernel space I store some information in that pages.
5.- In the user space process I mmap the device and read from it, but I
can not get the information that I stored there :-(


It's not working, and I can't understand why. When the process makes an
mmap on the device it doesn't complain, but the resulting mapping is not
correct, because I can't access the information that is contained in the
physical page.

If any of you can help me It would be apreciated,

thank you very much in advantage.

Best regards,
Rodrigo

-- 
Rodrigo Fernandez-Vizarra Bonet
    e-mail: rodrigofv@jazzfree.com

You still can avoid the GATES of hell, USE LINUX !!!
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Memoy Management

[Márcio Oliveira]

Hi all,

  Somebody can help me with some memory management issues (like Out Of 
Memory) in Linux kernel 2.4 (with some backports from 2.6 kernel. eg. 
Red Hat Enterprise Kernel) and SMP machines (4 processors) with a lot of 
memory (16GB)?

Thanks a lot.

Márcio.

Re: Memoy Management

[Arjan van de Ven]

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On Wed, 2005-07-20 at 10:10 -0300, Márcio Oliveira wrote:
> Hi all,
> 
>   Somebody can help me with some memory management issues (like Out Of 
> Memory) in Linux kernel 2.4 (with some backports from 2.6 kernel. eg. 
> Red Hat Enterprise Kernel) and SMP machines (4 processors) with a lot of 
> memory (16GB)?

I'm sure RH support will be able to help you with that; I doubt many
other people care about an ancient kernel like that, and a vendor one to
boot.

(Also I assume you are using the -hugemem kernel as the documentation
recommends you to do)


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Re: Memory Management

[Márcio Oliveira]

Arjan van de Ven wrote:

>I'm sure RH support will be able to help you with that; I doubt many
>other people care about an ancient kernel like that, and a vendor one to
>boot.
>
>(Also I assume you are using the -hugemem kernel as the documentation
>recommends you to do)
>
>  
>
Arjan,

   I'd like to know/understand more about memory management  on  Linux 
Kernel and I belive this concept is applyable to the Red Hat Linux Kernel.

  I have some doubts about the ZONE divison (DMA, NORMAL, HIGHMEM), 
Shared Memory utilization, HugeTLB feature and OOM with large memory and 
the kernel management of memory on SMP machines. I believe these 
features are common to the Linux kernel in general(Red Hat, Debian, 
SuSe, kernel.org), right?
   I read a tons of docs regarding symposiums, The Linux Memory 
Management Book and lots of docs about Oracle memory management but 
memory management still not clear to me.

  If somebody can help me...

Thanks.

Memory Management Question

[Márcio Oliveira]

Hi

Is HugeTBL proc memory parameters only to hugetlbfs "filesystem" or are 
these parameters affect ramfs, shm and tmpfs too?

What is the basic difference between ramfs, hugetlbfs, shm and tmpfs to 
the memory management / process VLM utilization?

thanks,

Márcio.