Messages in this thread | | | From | "Bob Picco" <> | Date | Fri, 5 May 2006 12:18:31 -0400 | Subject | Re: assert/crash in __rmqueue() when enabling CONFIG_NUMA |
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Dave Hansen wrote: [Fri May 05 2006, 10:57:44AM EDT] > On Fri, 2006-05-05 at 10:50 -0400, Bob Picco wrote: > > Dave Hansen wrote: [Fri May 05 2006, 10:33:10AM EDT] > > > 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. > > Ahhh. I hadn't made the ia64 connection. I wonder if it is worth > making CONFIG_HOLES_IN_ZONE say ia64 or something about vmem_map in it > somewhere. Might be worth at least a comment like this: > > + if (page_in_zone_hole(buddy)) /* noop on all but ia64 */ > + break; > + else if (page_zonenum(buddy) != page_zonenum(page)) > + break; > + else if (!page_is_buddy(buddy, order)) > break; /* Move the buddy up one level. */ > > BTW, wasn't the whole idea of discontig to have holes in zones (before > NUMA) without tricks like this? ;) Sure you could boot ia64 with just DISCONTIGMEM and no VIRTUAL_MEM_MAP. In fact that's exactly what I did to test code added in alloc_node_mem_map. Unfortunately I was missing 1Gb from free memory after booting. The missing 1Gb was consumed by reserved pages structures :) > > -- 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/
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