GFP_KERNEL doubt!! <was Tasklet doubt!>

[Sriram Narasimhan]

  Hello,

The problem of allocating more than 2.5 MB was actually more or less 
related to the physical memory left in the kernel.
But I moved the task which allocated the memory from the tasklet to the 
keventd and used kmalloc (GFP_KERNEL).

The first time I ran my module, it failed at the same 2.5 MB limit.
I restarted the system and tried it again, and I was able to allocate 5 
MB successfully.
I restarted the system and ran "free".
The report is as follows:
             total       used       free     shared    buffers     cached
Mem:         62264      30624      31640          0       8072      16096
-/+ buffers/cache:       6456      55808
Swap:       192772          0     192772

Then I ran gcc and compiled my code and then for the "free" report again.
The report is as follows:
             total       used       free     shared    buffers     cached
Mem:         62264      45320      16944          0       9256      28384
-/+ buffers/cache:       7680      54584
Swap:       192772          0     192772

I was able to notice that the physical memory had gone down though "gcc" 
had completed.
The time I ran my application, I had about 2.5M physical memory left, so 
I was able to allocate 2.5M.

What is happening ? What is the buffers/cache column and is there any 
way I could force the kernel to release the cached memory back to free 
physical ?
Is there any way I can allocate more than what is left free from the 
physical memory ?

Any pointers or suggestions would be very helpful.

Thank you.
Regards,
Sriram