process memory limitations

[Maimon Oded]

Hi,

I've a question about per process memory allocation limitation.

if i've a 32bit machine, with RHEL 4, what are the limitation of memory 
that each process can allocate?

if i've a 64bit machine, with RHEL 4, and i'm using a 32bit program, 
what are the limitation of memory that each process can allocate?

Thanks,

Oded.

[Jonathan Berry]

On 1/22/06, Oded Maimon  wrote:
> Hi,
>
> I've a question about per process memory allocation limitation.

You do realize this is a list for Fedora, not RHEL, right?  Please
point other RHEL questions to the RHEL list.  You will get more/better
help there.
> if i've a 32bit machine, with RHEL 4, what are the limitation of memory
> that each process can allocate?

That depends on if your kernel has the 4G/4G patch or not.  I think
that patch floated in and out of the Fedora kernels for a while there.
 Anyway, if you do it is 4 GB.  Otherwise, I believe the split is 3 GB
user 1 GB kernel, so 3 GB.
> if i've a 64bit machine, with RHEL 4, and i'm using a 32bit program,
> what are the limitation of memory that each process can allocate?

That's an interesting question and I'm not sure.  But after thinking
about it, pointers in a 32-bit program are, well, 32-bits wide.  So I
don't see how it could possibly address more than 32-bits worth of
space.  So my guess would be 4 GB again.  Now, a 64-bit program has a
whole lot more.  I don't remember how much, but I doubt the exact
number is relevant, as it is probably more space than any normal
computer could handle : ).

Also, these are address space limitations.  The limitation on the
amount of memory a process can allocate depends also on the size of
the text and stack needed.  ulimit may also be able to impose some
limit as well, though I'm not familiar with all of its capabilities.

Jonathan

[Maimon Oded]

i'm aware that this is a fedora list, but my question is linux kernel
question, and i didnt want to get an answer that is true only to fedora
versions (because i know they got more limitations then others)

thanks for the answer...

On 1/23/06, Jonathan Berry  wrote:
> On 1/22/06, Oded Maimon  wrote:
> > Hi,
> >
> > I've a question about per process memory allocation limitation.
>
> You do realize this is a list for Fedora, not RHEL, right?  Please
> point other RHEL questions to the RHEL list.  You will get more/better
> help there.
> > if i've a 32bit machine, with RHEL 4, what are the limitation of memory
> > that each process can allocate?
>
> That depends on if your kernel has the 4G/4G patch or not.  I think
> that patch floated in and out of the Fedora kernels for a while there.
> Anyway, if you do it is 4 GB.  Otherwise, I believe the split is 3 GB
> user 1 GB kernel, so 3 GB.
> > if i've a 64bit machine, with RHEL 4, and i'm using a 32bit program,
> > what are the limitation of memory that each process can allocate?
>
> That's an interesting question and I'm not sure.  But after thinking
> about it, pointers in a 32-bit program are, well, 32-bits wide.  So I
> don't see how it could possibly address more than 32-bits worth of
> space.  So my guess would be 4 GB again.  Now, a 64-bit program has a
> whole lot more.  I don't remember how much, but I doubt the exact
> number is relevant, as it is probably more space than any normal
> computer could handle : ).
>
> Also, these are address space limitations.  The limitation on the
> amount of memory a process can allocate depends also on the size of
> the text and stack needed.  ulimit may also be able to impose some
> limit as well, though I'm not familiar with all of its capabilities.
>
> Jonathan
>
> --
> fedora-list mailing list
> [e-mail]
> To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list

[Christofer C. Bell]

On 1/23/06, Maimon Oded  wrote:
> i'm aware that this is a fedora list, but my question is linux kernel
> question, and i didnt want to get an answer that is true only to fedora
> versions (because i know they got more limitations then others)

Can you elaborate on this "i know they got more limitations then
others" postulation of yours, please?

--
Chris

"I trust the Democrats to take away my money, which I can afford.  I
trust the Republicans to take away my freedom, which I cannot."

[Tom Mitchell]

On Mon, Jan 23, 2006 at 12:17:33AM +0200, Oded Maimon wrote:
> Date: Mon, 23 Jan 2006 00:17:33 +0200
> From: Oded Maimon 
> To: For users of Fedora Core releases 
> Subject: process memory limitations
> Reply-To: For users of Fedora Core releases
>
> Hi,
>
> I've a question about per process memory allocation limitation.
>
> if i've a 32bit machine, with RHEL 4, what are the limitation of memory 
> that each process can allocate?
>
> if i've a 64bit machine, with RHEL 4, and i'm using a 32bit program, 
> what are the limitation of memory that each process can allocate?

Allocate, malloc(?), sbrk(), heap, stack....
What programming language?

In general an signed int that lets you move +/_ inside
something will put a 2GB limit on common objects and
common programming practices.

If you are concerned about bounds you need to write a test case
that explores exactly what matters to you.

Search engines like Google are your friend.

https://www.redhat.com/en_us/USA/rhel/details/limits/

Tells me:
Maximum x86 per-process virtual address space 	
    Version 2.1 	Version 3 	Version 4
    3GB	 	Approx 4GB 	Approx 4GB