Messages in this thread Patch in this message | | | Date | Fri, 1 Jul 2011 18:23:27 +0200 | From | Tejun Heo <> | Subject | [PATCH x86/urgent 2/2] x86: Implement pfn -> nid mapping granularity check |
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Both SPARSEMEM and DISCONTIGMEM have limited granularity when mapping pfn to nid. If NUMA nodes are laid out such that the mapping cannot be accurate, boot will fail triggering BUG_ON() in mminit_verify_page_links().
On 32bit, it's 512MiB w/ PAE and SPARSEMEM. This seems to have been granular enough until commit 2706a0bf7b (x86, NUMA: Enable CONFIG_AMD_NUMA on 32bit too). Apparently, there is a machine which aligns NUMA nodes to 128MiB and has only AMD NUMA but not SRAT. As x86_64 has granularity of 128MiB, NUMA config worked fine on the machine; however, the commit enabled AMD NUMA config on 32bit too and the 512MiB granularity wasn't enough.
On node 0 totalpages: 2096615 DMA zone: 32 pages used for memmap DMA zone: 0 pages reserved DMA zone: 3927 pages, LIFO batch:0 Normal zone: 1740 pages used for memmap Normal zone: 220978 pages, LIFO batch:31 HighMem zone: 16405 pages used for memmap HighMem zone: 1853533 pages, LIFO batch:31 BUG: Int 6: CR2 (null) EDI (null) ESI 00000002 EBP 00000002 ESP c1543ecc EBX f2400000 EDX 00000006 ECX (null) EAX 00000001 err (null) EIP c16209aa CS 00000060 flg 00010002 Stack: f2400000 00220000 f7200800 c1620613 00220000 01000000 04400000 00238000 (null) f7200000 00000002 f7200b58 f7200800 c1620929 000375fe (null) f7200b80 c16395f0 00200a02 f7200a80 (null) 000375fe 00000002 (null) Pid: 0, comm: swapper Not tainted 2.6.39-rc5-00181-g2706a0b #17 Call Trace: [<c136b1e5>] ? early_fault+0x2e/0x2e [<c16209aa>] ? mminit_verify_page_links+0x12/0x42 [<c1620613>] ? memmap_init_zone+0xaf/0x10c [<c1620929>] ? free_area_init_node+0x2b9/0x2e3 [<c1607e99>] ? free_area_init_nodes+0x3f2/0x451 [<c1601d80>] ? paging_init+0x112/0x118 [<c15f578d>] ? setup_arch+0x791/0x82f [<c15f43d9>] ? start_kernel+0x6a/0x257
This patch implements node_map_pfn_alignment() which determines maximum internode alignment and update numa_register_memblks() to reject NUMA configuration if alignment exceeds the pfn -> nid mapping granularity of the memory model as determined by PAGES_PER_SECTION.
This makes the problematic machine boot w/ flatmem by rejecting the NUMA config and provides protection against crazy NUMA configurations.
Signed-off-by: Tejun Heo <tj@kernel.org> LKML-Reference: <20110628174613.GP478@escobedo.osrc.amd.com> Reported-and-Tested-by: Hans Rosenfeld <hans.rosenfeld@amd.com> Cc: Conny Seidel <conny.seidel@amd.com> --- arch/x86/mm/numa.c | 11 ++++++++++ include/linux/mm.h | 1 mm/page_alloc.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 66 insertions(+)
Index: work/arch/x86/mm/numa.c =================================================================== --- work.orig/arch/x86/mm/numa.c +++ work/arch/x86/mm/numa.c @@ -496,6 +496,7 @@ static bool __init numa_meminfo_cover_me static int __init numa_register_memblks(struct numa_meminfo *mi) { + unsigned long pfn_align; int i, nid; /* Account for nodes with cpus and no memory */ @@ -511,6 +512,16 @@ static int __init numa_register_memblks( /* for out of order entries */ sort_node_map(); + + /* check whether pfn -> nid mapping has enough granularity */ + pfn_align = node_map_pfn_alignment(); + if (pfn_align && pfn_align < PAGES_PER_SECTION) { + printk(KERN_WARNING "Node alignment %LuMB < min %LuMB, rejecting NUMA config\n", + (u64)pfn_align << PAGE_SHIFT >> 20, + (u64)PAGES_PER_SECTION << PAGE_SHIFT >> 20); + return -EINVAL; + } + if (!numa_meminfo_cover_memory(mi)) return -EINVAL; Index: work/include/linux/mm.h =================================================================== --- work.orig/include/linux/mm.h +++ work/include/linux/mm.h @@ -1313,6 +1313,7 @@ extern void remove_active_range(unsigned unsigned long end_pfn); extern void remove_all_active_ranges(void); void sort_node_map(void); +unsigned long node_map_pfn_alignment(void); unsigned long __absent_pages_in_range(int nid, unsigned long start_pfn, unsigned long end_pfn); extern unsigned long absent_pages_in_range(unsigned long start_pfn, Index: work/mm/page_alloc.c =================================================================== --- work.orig/mm/page_alloc.c +++ work/mm/page_alloc.c @@ -4585,6 +4585,60 @@ void __init sort_node_map(void) cmp_node_active_region, NULL); } +/** + * node_map_pfn_alignment - determine the maximum internode alignment + * + * This function should be called after node map is populated and sorted. + * It calculates the maximum power of two alignment which can distinguish + * all the nodes. + * + * For example, if all nodes are 1GiB and aligned to 1GiB, the return value + * would indicate 1GiB alignment with (1 << (30 - PAGE_SHIFT)). If the + * nodes are shifted by 256MiB, 256MiB. Note that if only the last node is + * shifted, 1GiB is enough and this function will indicate so. + * + * This is used to test whether pfn -> nid mapping of the chosen memory + * model has fine enough granularity to avoid incorrect mapping for the + * populated node map. + * + * Returns the determined alignment in pfn's. 0 if there is no alignment + * requirement (single node). + */ +unsigned long __init node_map_pfn_alignment(void) +{ + unsigned long accl_mask = 0, last_end = 0; + int last_nid = -1; + int i; + + for_each_active_range_index_in_nid(i, MAX_NUMNODES) { + int nid = early_node_map[i].nid; + unsigned long start = early_node_map[i].start_pfn; + unsigned long end = early_node_map[i].end_pfn; + unsigned long mask; + + if (!start || last_nid < 0 || last_nid == nid) { + last_nid = nid; + last_end = end; + continue; + } + + /* + * Start with a mask granular enough to pin-point to the + * start pfn and tick off bits one-by-one until it becomes + * too coarse to separate the current node from the last. + */ + mask = ~((1 << __ffs(start)) - 1); + while (mask && last_end <= (start & (mask << 1))) + mask <<= 1; + + /* accumulate all internode masks */ + accl_mask |= mask; + } + + /* convert mask to number of pages */ + return ~accl_mask + 1; +} + /* Find the lowest pfn for a node */ static unsigned long __init find_min_pfn_for_node(int nid) {
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