Messages in this thread Patch in this message | | | Subject | Re: [RFC/PATCH v2] mm: Introduce GFP_PANIC for non-failing allocations | From | Pekka Enberg <> | Date | Fri, 08 May 2009 17:34:41 +0300 |
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On Fri, 2009-05-08 at 10:29 -0400, Christoph Lameter wrote: > On Fri, 8 May 2009, Pekka Enberg wrote: > > > On Fri, 8 May 2009, Pekka Enberg wrote: > > > > +#define GFP_PANIC (__GFP_NOFAIL | __GFP_NORETRY | __GFP_NOMEMALLOC) > > > > On Fri, 2009-05-08 at 10:20 -0400, Christoph Lameter wrote: > > > So this means not retrying the allocation a couple of times? Not delving > > > into reserve pools? Such behavior is good for a allocation that causes a > > > panic if it fails? > > > > If you do GFP_KERNEL|GFP_PANIC, we will cond_resched() and retry if we > > made some progress. So yes, I think the behavior is good for early-boot > > call-sites that can't really fail anyway. > > Better make sure that GFP_PANIC is only used during early boot then. > > If memory is low on boot (due to node hotplug or some such thing, powerpc > may do evil tricks here) then the panic may trigger after the patch. > We would have just delved into the reserves a bit before.
Nah, it's probably better to drop __GFP_NOMEMALLOC instead. Does this look better?
Pekka
>From c91c70265545f2fcc727b4a0d37162b5aa0f5ecf Mon Sep 17 00:00:00 2001 From: Cyrill Gorcunov <gorcunov@openvz.org> Date: Fri, 8 May 2009 15:44:50 +0300 Subject: [PATCH] mm: Introduce GFP_PANIC for non-failing allocations
This patch introduces a GFP_PANIC flag that can be used as an annotation that a call to kmalloc() or alloc_pages() is expected to never fail. This is useful in early boot code, for example.
To save one GFP flag bit, use a combination of __GFP_NOFAIL, __GFP_NOREPEAT, and __GFP_NOMEMALLOC to make sure we always end up in the "nopage" path of the page allocator if an allocation fails.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org> Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi> --- include/linux/gfp.h | 1 + mm/page_alloc.c | 6 +++++- 2 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 0bbc15f..b34e6e5 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -70,6 +70,7 @@ struct vm_area_struct; #define GFP_HIGHUSER_MOVABLE (__GFP_WAIT | __GFP_IO | __GFP_FS | \ __GFP_HARDWALL | __GFP_HIGHMEM | \ __GFP_MOVABLE) +#define GFP_PANIC (__GFP_NOFAIL | __GFP_NORETRY) #ifdef CONFIG_NUMA #define GFP_THISNODE (__GFP_THISNODE | __GFP_NOWARN | __GFP_NORETRY) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e2f2699..de7f666 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1556,7 +1556,8 @@ nofail_alloc: zonelist, high_zoneidx, ALLOC_NO_WATERMARKS); if (page) goto got_pg; - if (gfp_mask & __GFP_NOFAIL) { + /* GFP_PANIC sets both flags */ + if ((gfp_mask & __GFP_NOFAIL) && !(gfp_mask & __GFP_NORETRY)) { congestion_wait(WRITE, HZ/50); goto nofail_alloc; } @@ -1670,6 +1671,9 @@ nopage: dump_stack(); show_mem(); } + if (unlikely(gfp_mask & GFP_PANIC)) + panic("Out of memory: %s order: %d, gfp_mask:0x%x\n", + p->comm, order, gfp_mask); got_pg: return page; } -- 1.5.6.3
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