Re: OOM behavior in constrained memory situations

[Andi Kleen <ak@suse.de>]

On Tuesday 07 February 2006 02:55, Christoph Lameter wrote:
> I just tried to oom a process that has restricted its mem allocation to 
> node 0 using a memory policy. Instead of an OOM the system began to swap 
> on node zero. The swapping is restricted to the zones passed to 
> __alloc_pages. It was thus swapping node zero alone.

Thanks for doing that work. It's needed imho and was on my todo list.


>  	switch (pol->policy) {
>  	case MPOL_DEFAULT:
>  		break;
> Index: linux-2.6.16-rc2/include/linux/mempolicy.h
> ===================================================================
> --- linux-2.6.16-rc2.orig/include/linux/mempolicy.h	2006-02-02 22:03:08.000000000 -0800
> +++ linux-2.6.16-rc2/include/linux/mempolicy.h	2006-02-06 17:07:41.000000000 -0800
> @@ -62,6 +62,7 @@ struct vm_area_struct;
>  struct mempolicy {
>  	atomic_t refcnt;
>  	short policy; 	/* See MPOL_* above */
> +	gfp_t gfp_flags;	/* flags ORed into gfp_flags for each allocation */

I don't think it's a good idea to add it to the struct mempolicy. I've tried to
make it as memory efficient as possibile and it would be a waste to add such
a mostly unused field. Better to pass that information around in some other way.

(in the worst case it could be a upper bit in policy, but I would prefer
function arguments I think) 

The rest looks good.

-Andi