On 2016/6/7 16:31, Ganapatrao Kulkarni wrote:
> On Tue, Jun 7, 2016 at 1:38 PM, Zhen Lei <thunder.leizhen@xxxxxxxxxx> wrote:
>> Some numa nodes may have no memory. For example:
>> 1. cpu0 on node0
>> 2. cpu1 on node1
>> 3. device0 access the momory from node0 and node1 take the same time.
>
> i am wondering, if access to both nodes is same, then why you need numa.
> the example you are quoting is against the basic principle of "numa"
> what is device0 here? cpu?
The device0 can also be a cpu. I drew a simple diagram:
cpu0 cpu1 cpu2/device0
| | |
| | |
DDR0 DDR1 No DIMM slots or no DIMM plugged
(node0) (node1) (node2)
>>
>> So, we can not simply classify device0 to node0 or node1, but we can
>> define a node2 which distances to node0 and node1 are the same.
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>> ---
>> arch/arm64/Kconfig | 4 ++++
>> arch/arm64/kernel/smp.c | 1 +
>> arch/arm64/mm/numa.c | 43 +++++++++++++++++++++++++++++++++++++++++--
>> 3 files changed, 46 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 05c1bf1..5904a62 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -581,6 +581,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>> def_bool y
>> depends on NUMA
>>
>> +config HAVE_MEMORYLESS_NODES
>> + def_bool y
>> + depends on NUMA
>> +
>> source kernel/Kconfig.preempt
>> source kernel/Kconfig.hz
>>
>> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
>> index d099306..9e15297 100644
>> --- a/arch/arm64/kernel/smp.c
>> +++ b/arch/arm64/kernel/smp.c
>> @@ -620,6 +620,7 @@ static void __init of_parse_and_init_cpus(void)
>> }
>>
>> bootcpu_valid = true;
>> + early_map_cpu_to_node(0, of_node_to_nid(dn));
>>
>> /*
>> * cpu_logical_map has already been
>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
>> index df5c842..d73b0a0 100644
>> --- a/arch/arm64/mm/numa.c
>> +++ b/arch/arm64/mm/numa.c
>> @@ -128,6 +128,14 @@ void __init early_map_cpu_to_node(unsigned int cpu, int nid)
>> nid = 0;
>>
>> cpu_to_node_map[cpu] = nid;
>> +
>> + /*
>> + * We should set the numa node of cpu0 as soon as possible, because it
>> + * has already been set up online before. cpu_to_node(0) will soon be
>> + * called.
>> + */
>> + if (!cpu)
>> + set_cpu_numa_node(cpu, nid);
>> }
>>
>> #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
>> @@ -215,6 +223,35 @@ int __init numa_add_memblk(int nid, u64 start, u64 end)
>> return ret;
>> }
>>
>> +static u64 __init alloc_node_data_from_nearest_node(int nid, const size_t size)
>> +{
>> + int i, best_nid, distance;
>> + u64 pa;
>> + DECLARE_BITMAP(nodes_map, MAX_NUMNODES);
>> +
>> + bitmap_zero(nodes_map, MAX_NUMNODES);
>> + bitmap_set(nodes_map, nid, 1);
>> +
>> +find_nearest_node:
>> + best_nid = NUMA_NO_NODE;
>> + distance = INT_MAX;
>> +
>> + for_each_clear_bit(i, nodes_map, MAX_NUMNODES)
>> + if (numa_distance[nid][i] < distance) {
>> + best_nid = i;
>> + distance = numa_distance[nid][i];
>> + }
>> +
>> + pa = memblock_alloc_nid(size, SMP_CACHE_BYTES, best_nid);
>> + if (!pa) {
>> + BUG_ON(best_nid == NUMA_NO_NODE);
>> + bitmap_set(nodes_map, best_nid, 1);
>> + goto find_nearest_node;
>> + }
>> +
>> + return pa;
>> +}
>> +
>> /**
>> * Initialize NODE_DATA for a node on the local memory
>> */
>> @@ -228,7 +265,9 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
>> pr_info("Initmem setup node %d [mem %#010Lx-%#010Lx]\n",
>> nid, start_pfn << PAGE_SHIFT, (end_pfn << PAGE_SHIFT) - 1);
>>
>> - nd_pa = memblock_alloc_try_nid(nd_size, SMP_CACHE_BYTES, nid);
>> + nd_pa = memblock_alloc_nid(nd_size, SMP_CACHE_BYTES, nid);
>> + if (!nd_pa)
>> + nd_pa = alloc_node_data_from_nearest_node(nid, nd_size);
>> nd = __va(nd_pa);
>>
>> /* report and initialize */
>> @@ -238,7 +277,7 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
>> if (tnid != nid)
>> pr_info(" NODE_DATA(%d) on node %d\n", nid, tnid);
>>
>> - node_data[nid] = nd;
>> + NODE_DATA(nid) = nd;
>> memset(NODE_DATA(nid), 0, sizeof(pg_data_t));
>> NODE_DATA(nid)->node_id = nid;
>> NODE_DATA(nid)->node_start_pfn = start_pfn;
>> --
>> 2.5.0
>>
>>
> Ganapat
>>
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>> linux-arm-kernel mailing list
>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
> .
>
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