kmalloc() memory is reserved or not?
I tried to print the amount of reserved memory before and after allocating 10 MB of memory using kmalloc(). But both shows the same.
Here is the code,
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/kdev_t.h>
#include <asm/page.h>
#include <asm/memory.h>
#include <linux/cdev.h>
#include <linux/device.h>
static int check_memory(void)
{
int i ;
int temp = 0;
int reserved;
struct page * pp;
unsigned long reserved_pages=0;
i = virt_to_phys(0xc0000000);
i >>= PAGE_SHIFT;
while (pfn_valid(i)) {
pp = pfn_to_page(i);
reserved = PageReserved(pp);
if(reserved)
reserved_pages++;
if ( ( temp != reserved ) || ( i == 0 ) )
printk("%08x reserved: %s\n", i << PAGE_SHIFT, reserved? "yes": "no");
temp = reserved;
++i;
}
printk("number of reserved pages = %d\n", reserved_pages);
printk("total memory used by kernel = %d\n", reserved_pages*(1 << PAGE_SHIFT));
return 0;
}
static int simple_init(void)
{
int i;
check_memory();
/* Allocating 10MB of memory */
for ( i = 0 ; i < 2560 ; i ++){
if( kmalloc(4096, GFP_KERNEL) == NULL)
printk("cannot alocate memory %d\n", i);
}
check_memory();
return 0;
}
static void simple_cleanup(void)
{
}
module_init(simple_init);
module_exit(simple_cleanup);
Any Idea?
Here is the output.
<4>[ 309.065732] number of reserved pages = 13009
<4>[ 309.065746] total memory used by kernel = 53284864
<4>[ 321.214470] number of reserved pages = 13009
<4>[ 321.214483] total memory used by kernel = 53284864
Arun
On Wed, Sep 29, 2010 at 12:43 AM, Arun KS <getarunks@xxxxxxxxx> wrote:
Just updating our simple_module to work on all the machines,
#include <asm/memory.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/kdev_t.h>
#include <asm/page.h>
#include <linux/cdev.h>
#include <linux/device.h>int i ;
static int simple_init(void)
{
int temp = 0;unsigned long reserved_pages=0;
int reserved;
struct page * pp;
i = virt_to_phys(0xc0000000);
i >>= PAGE_SHIFT;
if(reserved)
while (pfn_valid(i)) {
pp = pfn_to_page(i);
reserved = PageReserved(pp);
reserved_pages++;
printk("number of reserved pages = %d\n", reserved_pages);
if ( ( temp != reserved ) || ( i == 0 ) )
printk("%08x reserved: %s\n", i << PAGE_SHIFT,
reserved? "yes": "no");
temp = reserved;
++i;
}
printk("total memory used by kernel in bytes = %d\n",
reserved_pages*(1 << PAGE_SHIFT));
return 0;Thanks,
}
static void simple_cleanup(void)
{
}
module_init(simple_init);
module_exit(simple_cleanup);
Arun
On Tue, Sep 28, 2010 at 2:47 PM, Arun KS <getarunks@xxxxxxxxx> wrote:
> Hi Dave,
>
> Thanks for your reply.
>
> On Tue, Sep 28, 2010 at 1:00 PM, Dave Hylands <dhylands@xxxxxxxxx> wrote:
>> Hi Arun,
>>
>>>> I can definitely confirm that not all ARM processors start their RAM
>>>> at physical address zero.
>>>>
>>>> If you have a kernel module (or you can rebuild your kernel to add a
>>>> printk), you can have it print out the 4 bytes at virtual address
>>>> 0xC0004000. The top 3 nibbles of this first word will be the top 3
>>>> nibbles of the physical address of your first page of memory.
>>>>
>>>> So, something like:
>>>>
>>>> printk( "0x%08x\n", *(uint32_t *)0xc0004000 );
>>>
>>> I tried printing,
>>>
>>> printk( "0x%08x\n", *(uint32_t *)0xc0004000 );
>>> printk("0x%08x\n", virt_to_phys(0xc0004000));
>>>
>>> Output:
>>> 0x00000000
>>> 0x13004000
>>
>> Ok - so this tells me that your SDRAM starts at 0x13000000
>>
>> I realized that printing 0xc0004000 corresponds to memory location zero.
>>
>> What we really wanted was the MMU entry which correponds to virtual
>> address 0xc0000000. The high 3 nibbles is 0xc00, so we would have
>> needed to do
>>
>> printk( "0x%08x\n", *(uint32_t *)(0xc0004000 + ( 0xc00 * 4 ));
>>
>> and that should print
>>
>> 0x130xxxxx
>>
>>> So I initialized the variable "i" in the kernel module to 0x13004000.
>>> But still it is not entering the while loop.
>>
>> PFN's are equal to the physical address shifted right by 20.
>
> Is this value 12?
>
>>
>> So the PFN for 0x13004000 would be 0x130 or 304 (base 10)
>
> so PFN is 0x13004
>
> Here is the output of the module when i is initialized to 0x13004.
>
> <4>[ 1647.455344] 13004000 reserved: yes
> <4>[ 1647.455373] 13008000 reserved: no
> <4>[ 1647.455414] 1302c000 reserved: yes
> <4>[ 1647.456213] 136b4000 reserved: no
> <4>[ 1647.456241] 136b6000 reserved: yes
> <4>[ 1647.456461] 1385a000 reserved: no
> <4>[ 1647.457838] 143c5000 reserved: yes
> <4>[ 1647.462746] 16bf2000 reserved: no
> <4>[ 1647.462783] 16c00000 reserved: yes
> <4>[ 1647.463083] 16e50000 reserved: no
> <4>[ 1647.478204] 1ea0c000 reserved: yes
> <4>[ 1647.478246] 1ea0f000 reserved: no
> <4>[ 1647.478304] 1ea56000 reserved: yes
> <4>[ 1647.478331] 1ea57000 reserved: no
> <4>[ 1647.478391] 1eaa1000 reserved: yes
> <4>[ 1647.478416] 1eaa2000 reserved: no
> <4>[ 1647.478443] 1eaa3000 reserved: yes
> <4>[ 1647.478468] 1eaa4000 reserved: no
> <4>[ 1647.478499] 1eab0000 reserved: yes
> <4>[ 1647.478529] 1eab9000 reserved: no
> <4>[ 1647.480438] 1f9c0000 reserved: yes
> <4>[ 1647.480471] 1f9c9000 reserved: no
> <4>[ 1647.480591] 1fa94000 reserved: yes
> <4>[ 1647.480618] 1fa95000 reserved: no
> <4>[ 1647.480651] 1faa8000 reserved: yes
> <4>[ 1647.480678] 1faa9000 reserved: no
> <4>[ 1647.480756] 1fb1c000 reserved: yes
> <4>[ 1647.480784] 1fb20000 reserved: no
> <4>[ 1647.480826] 1fb46000 reserved: yes
> <4>[ 1647.480853] 1fb47000 reserved: no
> <4>[ 1647.480921] 1fba4000 reserved: yes
> <4>[ 1647.480948] 1fba6000 reserved: no
> <4>[ 1647.481391] 1ff28000 reserved: yes
> <4>[ 1647.481418] 1ff2b000 reserved: no
>
> Thanks for everyone. This helped me. :-)
>
> Arun
>
>>
>>> Makefile.boot is saying
>>>
>>> zreladdr-y := 0x13008000
>>> params_phys-y := 0x13000100
>>
>> This further confirms that physical memory starts at 0x13000000
>>
>> --
>> Dave Hylands
>> Shuswap, BC, Canada
>> http://www.DaveHylands.com/
>>
>
