* About kernel memory limit
@ 2011-11-10 14:23 Geraint Yang
2011-11-10 20:58 ` Dave Hylands
0 siblings, 1 reply; 9+ messages in thread
From: Geraint Yang @ 2011-11-10 14:23 UTC (permalink / raw)
To: kernelnewbies
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.
Any help will be appreaciated.
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* About kernel memory limit
2011-11-10 14:23 About kernel memory limit Geraint Yang
@ 2011-11-10 20:58 ` Dave Hylands
2011-11-11 4:44 ` Geraint Yang
0 siblings, 1 reply; 9+ messages in thread
From: Dave Hylands @ 2011-11-10 20:58 UTC (permalink / raw)
To: kernelnewbies
Hi,
On Thu, Nov 10, 2011 at 6:23 AM, Geraint Yang <geraint0923@gmail.com> 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
^ permalink raw reply [flat|nested] 9+ messages in thread
* About kernel memory limit
2011-11-10 20:58 ` Dave Hylands
@ 2011-11-11 4:44 ` Geraint Yang
2011-11-11 5:08 ` Haojian Zhuang
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: Geraint Yang @ 2011-11-11 4:44 UTC (permalink / raw)
To: kernelnewbies
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 ?
On Fri, Nov 11, 2011 at 4:58 AM, Dave Hylands <dhylands@gmail.com> wrote:
> Hi,
>
> On Thu, Nov 10, 2011 at 6:23 AM, Geraint Yang <geraint0923@gmail.com>
> 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
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* About kernel memory limit
2011-11-11 4:44 ` Geraint Yang
@ 2011-11-11 5:08 ` Haojian Zhuang
2011-11-11 5:15 ` Dave Stevens
2011-11-11 8:20 ` Dave Hylands
2 siblings, 0 replies; 9+ messages in thread
From: Haojian Zhuang @ 2011-11-11 5:08 UTC (permalink / raw)
To: kernelnewbies
On Fri, Nov 11, 2011 at 12:44 PM, Geraint Yang <geraint0923@gmail.com> wrote:
> 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 ?
>
Kernel can operate 896MB directly. If your physical memory is larger
than this memory size, you can use high memory. So kernel needs to map
them first, then use it. The mapped size is limited in 128MB at the
same time.
Thanks
Haojian
^ permalink raw reply [flat|nested] 9+ messages in thread
* About kernel memory limit
2011-11-11 4:44 ` Geraint Yang
2011-11-11 5:08 ` Haojian Zhuang
@ 2011-11-11 5:15 ` Dave Stevens
2011-11-11 5:28 ` Geraint Yang
2011-11-11 8:20 ` Dave Hylands
2 siblings, 1 reply; 9+ messages in thread
From: Dave Stevens @ 2011-11-11 5:15 UTC (permalink / raw)
To: kernelnewbies
Quoting Geraint Yang <geraint0923@gmail.com>:
> 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@gmail.com> wrote:
>
>> Hi,
>>
>> On Thu, Nov 10, 2011 at 6:23 AM, Geraint Yang <geraint0923@gmail.com>
>> 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
^ permalink raw reply [flat|nested] 9+ messages in thread
* About kernel memory limit
2011-11-11 5:15 ` Dave Stevens
@ 2011-11-11 5:28 ` Geraint Yang
2011-11-11 5:46 ` adheer chandravanshi
0 siblings, 1 reply; 9+ messages in thread
From: Geraint Yang @ 2011-11-11 5:28 UTC (permalink / raw)
To: kernelnewbies
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@uniserve.com> wrote:
> Quoting Geraint Yang <geraint0923@gmail.com>:
>
> 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@gmail.com> wrote:
>>
>> Hi,
>>>
>>> On Thu, Nov 10, 2011 at 6:23 AM, Geraint Yang <geraint0923@gmail.com>
>>> 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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* About kernel memory limit
2011-11-11 5:28 ` Geraint Yang
@ 2011-11-11 5:46 ` adheer chandravanshi
0 siblings, 0 replies; 9+ messages in thread
From: adheer chandravanshi @ 2011-11-11 5:46 UTC (permalink / raw)
To: kernelnewbies
Try this command:
dmesg | grep Memory
For me the output is:
[ 0.000000] Memory: 2007408k/2051636k available (4678k kernel code, 42932k reserved, 2124k data, 668k init, 1142332k highmem)
Look here for more details:
https://bbs.archlinux.org/viewtopic.php?id=14412
~ Adheer
From: geraint0923@gmail.com
Date: Fri, 11 Nov 2011 13:28:53 +0800
Subject: Re: About kernel memory limit
To: geek at uniserve.com
CC: dhylands at gmail.com; kernelnewbies at kernelnewbies.org
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@uniserve.com> wrote:
Quoting Geraint Yang <geraint0923@gmail.com>:
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@gmail.com> wrote:
Hi,
On Thu, Nov 10, 2011 at 6:23 AM, Geraint Yang <geraint0923@gmail.com>
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
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies at kernelnewbies.org
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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* About kernel memory limit
2011-11-11 4:44 ` Geraint Yang
2011-11-11 5:08 ` Haojian Zhuang
2011-11-11 5:15 ` Dave Stevens
@ 2011-11-11 8:20 ` Dave Hylands
2011-11-11 8:40 ` Geraint Yang
2 siblings, 1 reply; 9+ messages in thread
From: Dave Hylands @ 2011-11-11 8:20 UTC (permalink / raw)
To: kernelnewbies
Hi Geraint,
On Thu, Nov 10, 2011 at 8:44 PM, Geraint Yang <geraint0923@gmail.com> wrote:
> 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 ?
There is a certain amount (exact amount depends on the architecture
and configuration) that can be accessed directly all of the time.
Then there is high memory, which can be accessed using kmap/kunmap.
See http://linux-mm.org/HighMemory
If you have a 64-bit system, then you can access all of the memory directly.
--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com
^ permalink raw reply [flat|nested] 9+ messages in thread
* About kernel memory limit
2011-11-11 8:20 ` Dave Hylands
@ 2011-11-11 8:40 ` Geraint Yang
0 siblings, 0 replies; 9+ messages in thread
From: Geraint Yang @ 2011-11-11 8:40 UTC (permalink / raw)
To: kernelnewbies
Thank you !
I will try kmap/kunmap later.
On Fri, Nov 11, 2011 at 4:20 PM, Dave Hylands <dhylands@gmail.com> wrote:
> Hi Geraint,
>
> On Thu, Nov 10, 2011 at 8:44 PM, Geraint Yang <geraint0923@gmail.com>
> wrote:
> > 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 ?
>
> There is a certain amount (exact amount depends on the architecture
> and configuration) that can be accessed directly all of the time.
>
> Then there is high memory, which can be accessed using kmap/kunmap.
> See http://linux-mm.org/HighMemory
>
> If you have a 64-bit system, then you can access all of the memory
> directly.
>
> --
> Dave Hylands
> Shuswap, BC, Canada
> http://www.davehylands.com
>
--
Geraint Yang
Tsinghua University Department of Computer Science and Technology
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2011-11-10 14:23 About kernel memory limit Geraint Yang
2011-11-10 20:58 ` Dave Hylands
2011-11-11 4:44 ` Geraint Yang
2011-11-11 5:08 ` Haojian Zhuang
2011-11-11 5:15 ` Dave Stevens
2011-11-11 5:28 ` Geraint Yang
2011-11-11 5:46 ` adheer chandravanshi
2011-11-11 8:20 ` Dave Hylands
2011-11-11 8:40 ` Geraint Yang
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