Messages in this thread | | | Date | Thu, 11 Feb 2010 01:19:40 -0800 (PST) | From | David Rientjes <> | Subject | Re: [patch 6/7 -mm] oom: avoid oom killer for lowmem allocations |
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On Wed, 10 Feb 2010, Rik van Riel wrote:
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1914,6 +1914,9 @@ rebalance: > > * running out of options and have to consider going OOM > > */ > > if (!did_some_progress) { > > + /* The oom killer won't necessarily free lowmem */ > > + if (high_zoneidx< ZONE_NORMAL) > > + goto nopage; > > if ((gfp_mask& __GFP_FS)&& !(gfp_mask& __GFP_NORETRY)) { > > if (oom_killer_disabled) > > goto nopage; > > Are there architectures that only have one memory zone? >
It actually ends up not to matter because of how gfp_zone() is implemented (and you can do it with mem= on architectures with larger ZONE_DMA zones such as ia64). ZONE_NORMAL is always guaranteed to be defined regardless of architecture or configuration because it's the default zone for memory allocation unless specified by a bit in GFP_ZONEMASK, it doesn't matter whether it actually has memory or not. high_zoneidx in this case is just gfp_zone(gfp_flags) which always defaults to ZONE_NORMAL when one of the GFP_ZONEMASK bits is not set. Thus, the only way to for the conditional in this patch to be true is when __GFP_DMA, or __GFP_DMA32 for x86_64, is passed to the page allocator and CONFIG_ZONE_DMA or CONFIG_ZONE_DMA32 is enabled, respectively.
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