Re: [PATCH v3 07/13] x86, numa, mem-hotplug: Mark nodes which thekernel resides in.
From: Tang Chen
Date: Mon Jun 03 2013 - 03:33:26 EST
Hi Vasilis,
On 06/01/2013 12:24 AM, Vasilis Liaskovitis wrote:
......
+void __init_memblock memblock_mark_kernel_nodes()
+{
+ int i, nid;
+ struct memblock_type *reserved =&memblock.reserved;
+
+ for (i = 0; i< reserved->cnt; i++)
+ if (reserved->regions[i].flags == MEMBLK_FLAGS_DEFAULT) {
+ nid = memblock_get_region_node(&reserved->regions[i]);
+ node_set(nid, memblock_kernel_nodemask);
+ }
+}
I think there is a problem here because memblock_set_region_node is sometimes
called with nid == MAX_NUMNODES. This means the correct node is not properly
masked in the memblock_kernel_nodemask bitmap.
E.g. in a VM test, memblock_mark_kernel_nodes with extra pr_warn calls iterates
over the following memblocks (ranges below are memblks base-(base+size)):
[ 0.000000] memblock_mark_kernel_nodes nid=64 0x00000000000000-0x00000000010000
[ 0.000000] memblock_mark_kernel_nodes nid=64 0x00000000098000-0x00000000100000
[ 0.000000] memblock_mark_kernel_nodes nid=64 0x00000001000000-0x00000001a5a000
[ 0.000000] memblock_mark_kernel_nodes nid=64 0x00000037000000-0x000000377f8000
where MAX_NUMNODES is 64 because CONFIG_NODES_SHIFT=6.
The ranges above belong to node 0, but the node's bit is never marked.
With a buggy bios that marks all memory as hotpluggable, this results in a
panic, because both checks against hotpluggable bit and memblock_kernel_bitmask
(in early_mem_hotplug_init) fail, the numa regions have all been merged together
and memblock_reserve_hotpluggable is called for all memory.
With a correct bios (some part of initial memory is not hotplug-able) the kernel
can boot since the hotpluggable bit check works ok, but extra dimms on node 0
will still be allowed to be in MOVABLE_ZONE.
OK, I see the problem. But would you please give me a call trace that
can show
how this could happen. I think the memory block info should be the same as
numa_meminfo. Can we fix the caller to make it set nid correctly ?
Actually this behaviour (being able to have MOVABLE memory on nodes with kernel
reserved memblocks) sort of matches the policy I requested in v2 :). But i
suspect that is not your intent i.e. you want memblock_kernel_nodemask_bitmap to
prevent movable reservations for the whole node where kernel has reserved
memblocks.
I intended to set the whole node which the kernel resides in as
un-hotpluggable.
Is there a way to get accurate nid information for memblocks at early boot? I
suspect pfn_to_nid doesn't work yet at this stage (i got a panic when I
attempted iirc)
In such an early time, I think we can only get nid from numa_meminfo. So
as I
said above, I'd like to fix this problem by making memblock has correct nid.
And I read the patch below. I think if we get nid from numa_meminfo,
than we
don't need to call memblock_get_region_node().
Thanks. :)
I used the hack below but it depends on CONFIG_NUMA, hopefully there is a
cleaner general way:
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index cfd8c2f..af8ad2a 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -133,6 +133,19 @@ void __init setup_node_to_cpumask_map(void)
pr_debug("Node to cpumask map for %d nodes\n", nr_node_ids);
}
+int __init numa_find_range_nid(u64 start, u64 size)
+{
+ unsigned int i;
+ struct numa_meminfo *mi =&numa_meminfo;
+
+ for (i = 0; i< mi->nr_blks; i++) {
+ if (start>= mi->blk[i].start&& start + size -1<= mi->blk[i].end)
+ return mi->blk[i].nid;
+ }
+ return -1;
+}
+EXPORT_SYMBOL(numa_find_range_nid);
+
static int __init numa_add_memblk_to(int nid, u64 start, u64 end,
bool hotpluggable,
struct numa_meminfo *mi)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 77a71fb..194b7c7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1600,6 +1600,9 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
unsigned long start, unsigned long end);
#endif
+#ifdef CONFIG_NUMA
+int __init numa_find_range_nid(u64 start, u64 size);
+#endif
struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t);
diff --git a/mm/memblock.c b/mm/memblock.c
index a6b7845..284aced 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -834,15 +834,26 @@ int __init_memblock memblock_set_node(phys_addr_t base, phys_addr_t size,
void __init_memblock memblock_mark_kernel_nodes()
{
- int i, nid;
+ int i, nid, tmpnid;
struct memblock_type *reserved =&memblock.reserved;
for (i = 0; i< reserved->cnt; i++)
if (reserved->regions[i].flags == MEMBLK_FLAGS_DEFAULT) {
nid = memblock_get_region_node(&reserved->regions[i]);
+ if (nid == MAX_NUMNODES) {
+ tmpnid = numa_find_range_nid(reserved->regions[i].base,
+ reserved->regions[i].size);
+ if (tmpnid>= 0)
+ nid = tmpnid;
+ }
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index e862311..84d6e64 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -667,11 +667,7 @@ static bool srat_used __initdata;
*/
static void __init early_x86_numa_init(void)
{
- /*
- * Need to find out which nodes the kernel resides in, and arrange
- * them as un-hotpluggable when parsing SRAT.
- */
- memblock_mark_kernel_nodes();
if (!numa_off) {
#ifdef CONFIG_X86_NUMAQ
@@ -779,6 +775,12 @@ void __init early_initmem_init(void)
load_cr3(swapper_pg_dir);
__flush_tlb_all();
+ /*
+ * Need to find out which nodes the kernel resides in, and arrange
+ * them as un-hotpluggable when parsing SRAT.
+ */
+
+ memblock_mark_kernel_nodes();
early_mem_hotplug_init();
early_memtest(0, max_pfn_mapped<<PAGE_SHIFT);
--
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