Preemption patch problem

[Roger Larsson]

On Thursday 21 April 2005 12.08, Björn Östby wrote:
> Greetings.
>
> I have been struggling with the famous preemption patch (from Robert Love)
> the past few days. Im using mpc823e and tried with kernels
> 2.4.{18,21,22,23}. The patch applies flawless and so on, but when the
> kernel is up and running strange memory problems start to appear like:
>
> _alloc_pages: 0-order allocation failed (gfp=0x1d2/0)

[
   #define __GFP_DMA       0x01
* #define __GFP_HIGHMEM   0x02
* #define __GFP_WAIT      0x10    /* Can wait and reschedule? */
   #define __GFP_HIGH      0x20    /* Should access emergency pools? */
* #define __GFP_IO        0x40    /* Can start low memory physical IO? */
* #define __GFP_HIGHIO    0x80    /* Can start high mem physical IO? */
* #define __GFP_FS        0x100   /* Can call down to low-level FS? */

- - -
#define GFP_HIGHUSER    (             __GFP_WAIT | __GFP_IO | __GFP_HIGHIO | 
__GFP_FS | __GFP_HIGHMEM)
- - -
]

So page_alloc is called with GFP_HIGHUSER, from where and why?

Try to find out what is causing this, set the 'vm_gfp_debug'
see 'linux/mm/page_alloc.c'

>
> Right, so... It seems like a giant memory leak of some sort, cause when I
> run programs the kernel goes ballistic and starts reaping processes:
>
> "VM: Killing process <name>"

Well the problem is that it actually is not getting any memory. It might be
code that retries to allocate memory when there really are none (you probably
do not use swap)

>
> Eventually it comes down to "VM: killing init" and then it's curtains.
>
> I know that these problems is caused by the patch since the kernel runs
> smooth without the patch applied. Does anyone have a clue what to do here
> (beside let go of the patch)?

Analyze memory usage on the working non patched kernel.

/RogerL