Il 01/10/2010 9.51, Arun KS wrote:
Hello,
kmalloc() memory is reserved or not?
No, kmalloc memory is not reserved. The buddy allocator, which is
eventually used by kmalloc, use only pages NOT reserved and don't mark
the pages "reserved" when these are allocated.
In other words "reserved" bit is set only during boot time and I don't
think is ever modified later.
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
<mailto:getarunks@xxxxxxxxx>> wrote:
Just updating our simple_module to work on all the machines,
#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 simple_init(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 in bytes = %d\n",
reserved_pages*(1 << PAGE_SHIFT));
return 0;
}
static void simple_cleanup(void)
{
}
module_init(simple_init);
module_exit(simple_cleanup);
Thanks,
Arun
On Tue, Sep 28, 2010 at 2:47 PM, Arun KS <getarunks@xxxxxxxxx
<mailto:getarunks@xxxxxxxxx>> wrote:
> Hi Dave,
>
> Thanks for your reply.
>
> On Tue, Sep 28, 2010 at 1:00 PM, Dave Hylands <dhylands@xxxxxxxxx
<mailto: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/
>>
>
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