On Wed, Jun 8, 2016 at 7:46 AM, Leizhen (ThunderTown) <thunder.leizhen@xxxxxxxxxx> wrote: > > > On 2016/6/7 22:01, Ganapatrao Kulkarni wrote: >> 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? > If opened HAVE_MEMORYLESS_NODES, it will pick the nearest node for the cpus on > memoryless node. i see couple of arch enabled HAVE_MEMORYLESS_NODES, but i don't see any code in arch specific numa code for this. is that means the core code will take care of this? > > For example, in include/linux/topology.h > #ifdef CONFIG_HAVE_MEMORYLESS_NODES > ... > static inline int cpu_to_mem(int cpu) > { > return per_cpu(_numa_mem_, cpu); > } > ... > #else > ... > static inline int cpu_to_mem(int cpu) > { > return cpu_to_node(cpu); > } > ... > #endif > >> 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. > I also considered put these code(include HAVE_SETUP_PER_CPU_AREA) into drivers/of/of_numa.c, > but if I do that, it will make acpi numa dependent on of numa. numa core/common code is mainly in directory mm/ drivers/of/of_numa.c implements only device tree numa binding. > >> dont you think common code will take care of this? when you define >> HAVE_MEMORYLESS_NODES > > I have searched CONFIG_HAVE_MEMORYLESS_NODES in *.c, but did not find the relevant content. > So maybe other ARCHs also missed this. as mentioned above, arch code may not need any changes for this. > >> >>>>> /** >>>>> * 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. > Yes, the function is OK, but the performance is not. > > Suppose there are 3 nodes: > 1. cpu0 on node0, cpu1 on node1, cpu2 on node2. > 2. cpu2 access the memory on node1 take 1us, but access the memory on node1 take 5us. > That is, distance[2,1] is shorter than distance[2,0]. > 3. And node2 is a memoryless node. > > So if NODE_DATA(2) allocated from node0, it will take more time than allocted from node1 at run time. > Because NODE_DATA will be accessed at run time. > >> >>>>> + 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 >>>> >>>> . >>>> >>> >> >> . >> > thanks Ganapat -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html