Re: About kernel memory limit

[Geraint Yang <geraint0923@xxxxxxxxx>]

Thanks. 
But I think that command 'free' just tell the memory used in kernel space and user space.It is still unknown to us that how much memory is used by kernel.

On Fri, Nov 11, 2011 at 1:15 PM, Dave Stevens <geek@xxxxxxxxxxxx> wrote:

Quoting Geraint Yang <geraint0923@xxxxxxxxx>:

Hi Dave,
Thank you for your help !
Does it mean that I could use all of the memory my computer has? But one of
my classmates told me that kernel could only use 1G from a 4G
memory.computer...Is there anything I have misunderstood ?

I'm sitting in front of a Ubuntu box with 8G installed, uname -a shows:

Linux roger-System-Product-Name 3.0.0-12-generic #20-Ubuntu SMP Fri Oct 7 14:56:25 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

so kernel 3 and free: shows
            total       used       free     shared    buffers     cached
Mem:       8192500    2907656    5284844          0     162060    1915540
-/+ buffers/cache:     830056    7362444
Swap:      7812092          0    7812092

so 2.9G of 8 in use

Dave

On Fri, Nov 11, 2011 at 4:58 AM, Dave Hylands <dhylands@xxxxxxxxx> wrote:

Hi,

On Thu, Nov 10, 2011 at 6:23 AM, Geraint Yang <geraint0923@xxxxxxxxx>
wrote:
> Hi there,
> I am a newbie to Linux kernel programming. I am going to make a module
> which will cost much memory in kernel, I just want to know how much
> memory I can get by calling memory allocate API in kernel.

All of it.

>From kernel space, you can completely exhaust memory to the point of
making your system unusable.

>From kernel space you have vmalloc memory and kmalloc memory (plus a
couple other memory spaces). Depending on how things are configured,
it's possible to exhaust vmalloc memory even though there is memory
available to be kmalloc'd.

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

--
Geraint Yang
Tsinghua University Department of Computer Science and Technology

--
It is told that such are the aerodynamics and wing loading of the bumblebee that, in principle, it cannot fly...if all this be true...life among bumblebees must bear a remarkable resemblance to life in the United States.

-- John Kenneth Galbraith, in American Capitalism: The Concept of Countervailing Power

--

Geraint Yang
Tsinghua University Department of Computer Science and Technology

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