On Tue, Jun 7, 2016 at 6:27 PM, Leizhen (ThunderTown)
<thunder.leizhen@xxxxxxxxxx> wrote:
>
>
> 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)
>
thanks for the clarification. your example is for 3 node system, where
third node is memory less node.
do you see any issue in supporting this topology with existing code?
I think, this use case should be supported with present code.
>>>
>>> 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;
>>> +}
>>> +
why do we need this function in arch specific code.
dont you think common code will take care of this? when you define
HAVE_MEMORYLESS_NODES
>>> /**
>>> * 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);
this function try to allocate from a nid, if fails, it allocates from
node 0(local node).
this is ok for memory less node i guess.
>>> + 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
>>>
>>> _______________________________________________
>>> linux-arm-kernel mailing list
>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>
>> .
>>
>
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