lkml.org 
[lkml]   [2006]   [May]   [5]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
From"Bob Picco" <>
DateFri, 5 May 2006 10:50:18 -0400
SubjectRe: assert/crash in __rmqueue() when enabling CONFIG_NUMA
Dave Hansen wrote:	[Fri May 05 2006, 10:33:10AM EDT]
> On Fri, 2006-05-05 at 09:55 -0400, Bob Picco wrote:
> > -               if (!page_is_buddy(buddy, order))
> > +               if (page_in_zone_hole(buddy))
> > +                       break;
> > +               else if (page_zonenum(buddy) != page_zonenum(page))
> > +                       break;
> > +               else if (!page_is_buddy(buddy, order))
> >                         break;          /* Move the buddy up one level. */ 
> 
> The page_zonenum() checks look good, but I'm not sure I understand the
> page_in_zone_hole() part.  If a page is in a hole in a zone, it will
> still have a valid mem_map entry, right?  It should also never have been
> put into the allocator, so it also won't ever be coalesced.  
This has always been subtle and not too revealing.  It probably should
have a comment. The page_in_zone_hole check is for ia64 
VIRTUAL_MEM_MAP. You might compute a page structure which is in a hole not 
backed by memory; an unallocated page which covers pages structures. 
VIRTUAL_MEM_MAP uses a contiguous virtual region with virtual space holes
not backed by memory. Take a look at ia64_pfn_valid.
> 
> I'm a bit confused. :(
> 
> BTW, I like the idea of just aligning HIGHMEM's start because it has no
> runtime cost.  Buuuuut, it is still just a shift and compare of the two
> page->flags, which should already be (or will soon anyway be) in the
> cache.
Yes. I'll defer to Andy whether he wants the zonenum check or to align
HIGHMEM corrrectly.
> 
> -- Dave
> 
bob
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-05-05 14:52    [from the cache]
©2003-2008