Re: Regarding memory fragmentation using malloc....

[AmÃrico Wang]

On Wed, Apr 13, 2011 at 2:54 PM, Pintu Agarwal <pintu_agarwal@xxxxxxxxx> wrote:
> Dear All,
>
> I am trying to understand how memory fragmentation occurs in linux using many malloc calls.
> I am trying to reproduce the page fragmentation problem in linux 2.6.29.x on a linux mobile(without Swap) using a small malloc(in loop) test program of BLOCK_SIZE (64*(4*K)).
> And then monitoring the page changes in /proc/buddyinfo after each operation.
> From the output I can see that the page values under buddyinfo keeps changing. But I am not able to relate these changes with my malloc BLOCK_SIZE.
> I mean with my BLOCK_SIZE of (2^6 x 4K ==> 2^6 PAGES) the 2^6 th block under /proc/buddyinfo should change. But this is not the actual behaviour.
> Whatever is the blocksize, the buddyinfo changes only for 2^0 or 2^1 or 2^2 or 2^3.
>
> I am trying to measure the level of fragmentation after each page allocation.
> Can somebody explain me in detail, how actually /proc/buddyinfo changes after each allocation and deallocation.
>

What malloc() sees is virtual memory of the process, while buddyinfo
shows physical memory pages.

When you malloc() 64K memory, the kernel may not allocate a 64K
physical memory at one time
for you.

Thanks.
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