Messages in this thread | | | From | "Bob Picco" <> | Date | Thu, 4 May 2006 11:46:52 -0400 | Subject | Re: assert/crash in __rmqueue() when enabling CONFIG_NUMA |
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Dave Hansen wrote: [Thu May 04 2006, 11:21:06AM EDT] > I haven't thought through it completely, but these two lines worry me: > > > + start = pgdat->node_start_pfn & ~((1 << (MAX_ORDER - 1)) - 1); > > + end = start + pgdat->node_spanned_pages; > > Should the "end" be based off of the original "start", or the aligned > "start"? Yes. I failed to quilt refresh before sending. You mean end should be end = pgdat->node_start_pfn + pgdat->node_spanned_pages before rounding up. > > (using decimal math to make it easy) ... > > Let's say that MAX_ORDER comes out to be 10 pages. node_start_pfn is 9, > and the node's end pfn is 21. node_spanned_pages will be 12. "start" > will get rounded down to 0. "end" will be "start" (0) + > node_spanned_pages (12), so 12. "end" then gets rounded up to 20. > However, this is not sufficient space for the mem_map as the node > *actually* ended at 21. > > I think that "end" needs to be calculated without rounding down the > start_pfn, or the node_spanned_pages number needs to be rounded up in > the same way that "end" is. > > Does that sound right? Yes. > > Also, it might look nicer if there was an intermediate variable > something like this: > > #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1)) Yes. > > Take a look at the loop below, I've also used ALIGN() from kernel.h for > the "end" alignment. I think it is just a drop-in replacement. > > /* ia64 gets its own node_mem_map, before this, without bootmem */ > if (!pgdat->node_mem_map) { > unsigned long size, start, end; > struct page *map; > > /* > * The zone's endpoints aren't required to be MAX_ORDER > * aligned but the node_mem_map endpoints must be in order > * for the buddy allocator to function correctly. > */ > start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1); end = pgdat->node_start_pfn + pgdat->node_spanned_pages; > end = start + pgdat->node_spanned_pages; > end = ALIGN(end, MAX_ORDER_NR_PAGES); > size = (end - start) * sizeof(struct page); > map = alloc_remap(pgdat->node_id, size); > if (!map) > map = alloc_bootmem_node(pgdat, size); > pgdat->node_mem_map = map + (pgdat->node_start_pfn - start); > } > > -- 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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