Re: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag

David Rientjes
2009-05-04T20:02:30Z

On Mon, 4 May 2009, Rafael J. Wysocki wrote:

> Index: linux-2.6/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.orig/mm/page_alloc.c
> +++ linux-2.6/mm/page_alloc.c
> @@ -1599,7 +1599,8 @@ nofail_alloc:
> zonelist, high_zoneidx, alloc_flags);
> if (page)
> goto got_pg;
> - } else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
> + } else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)
> + && !(gfp_mask & __GFP_NO_OOM_KILL)) {
> if (!try_set_zone_oom(zonelist, gfp_mask)) {
> schedule_timeout_uninterruptible(1);
> goto restart;
> Index: linux-2.6/include/linux/gfp.h
> ===================================================================
> --- linux-2.6.orig/include/linux/gfp.h
> +++ linux-2.6/include/linux/gfp.h
> @@ -51,8 +51,9 @@ struct vm_area_struct;
> #define __GFP_THISNODE ((__force gfp_t)0x40000u)/* No fallback, no policies */
> #define __GFP_RECLAIMABLE ((__force gfp_t)0x80000u) /* Page is reclaimable */
> #define __GFP_MOVABLE ((__force gfp_t)0x100000u) /* Page is movable */
> +#define __GFP_NO_OOM_KILL ((__force gfp_t)0x200000u) /* Don't invoke out_of_memory() */
>
> -#define __GFP_BITS_SHIFT 21 /* Room for 21 __GFP_FOO bits */
> +#define __GFP_BITS_SHIFT 22 /* Number of __GFP_FOO bits */
> #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
>
> /* This equals 0, but use constants in case they ever change */
>

Yeah, that's much better, thanks. There's currently concerns about adding
a new gfp flag in another thread (__GFP_PANIC), though, so you might find
some resistance in adding a flag with a very specific and limited use cae.

I think you might have better luck in doing

struct zone *z;

for_each_populated_zone(z)
zone_set_flag(z, ZONE_OOM_LOCKED);

if all other tasks are really in D state at this point since oom killer
serialization is done with try locks in the page allocator. This is
equivalent to __GFP_NO_OOM_KILL.