INFO REQ: Clarification of Memory Management

INFO REQ: Clarification of Memory Management

[Joseph D. Wagner]

I'm a little confused about the way the Linux kernel allocates memory, and
I'm hoping someone could clarify this for me.

Does the __get_free_pages() function eventually call the kmalloc() function?
Or does the kmalloc() function eventually call the __get_free_pages()
function?  Or are these two totally separate functions for different
purposes?

Which of these functions can be called by user process for the purpose of
allocating memory for that user process?

TIA

Joseph Wagner

Flames will be directed to /dev/null

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Re: INFO REQ: Clarification of Memory Management

[Steven Smith]

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> Does the __get_free_pages() function eventually call the kmalloc() function?
> Or does the kmalloc() function eventually call the __get_free_pages()
> function?  Or are these two totally separate functions for different
> purposes?
kmalloc() will eventually call get_free_pages(), but you really
shouldn't ever need to know that, unless you're fiddling with the
implementations of either function.

Note that, even though kmalloc() uses get_free_pages() to allocate
memory, it performs various other bookkeeping tasks, and so the two
types of memory allocations really can't be mixed.

> Which of these functions can be called by user process for the purpose of
> allocating memory for that user process?
Neither; use malloc() in userspace. (Or the new operator if you're using
C++)

Steven Smith,
sos22@cam.ac.uk.

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Re: INFO REQ: Clarification of Memory Management

[Ken Moffat]

On Fri, 6 Dec 2002, Joseph D. Wagner wrote:

> I'm a little confused about the way the Linux kernel allocates memory, and
> I'm hoping someone could clarify this for me.
> 
> Does the __get_free_pages() function eventually call the kmalloc() function?
> Or does the kmalloc() function eventually call the __get_free_pages()
> function?  Or are these two totally separate functions for different
> purposes?
> 
> Which of these functions can be called by user process for the purpose of
> allocating memory for that user process?
>

 Unless *I'm* totally lost here (which is very possible) you are asking
about functions which are internal to the kernel and not for direct use
from userspace.

Ken
 
> TIA
> 
> Joseph Wagner
> 
> Flames will be directed to /dev/null
> 

-- 
 Out of the darkness a voice spake unto me, saying "smile, things could be
worse". So I smiled, and lo, things became worse.



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