Messages in this thread | | | Date | Fri, 08 May 2009 10:37:02 -0400 | From | Rik van Riel <> | Subject | Re: [RFC/PATCH v2] mm: Introduce GFP_PANIC for non-failing allocations |
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Pekka Enberg wrote: > 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);
Do you mean ((gfp_mask & GFP_PANIC) == GFP_PANIC)) ?
> @@ -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);
Ditto here.
-- All rights reversed.
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