Re: [PATCH v7 09/14] arm64/numa: support HAVE_SETUP_PER_CPU_AREA

Leizhen (ThunderTown)
2016-08-27T10:07:21Z

On 2016/8/26 21:28, Will Deacon wrote:
> On Wed, Aug 24, 2016 at 03:44:48PM +0800, Zhen Lei wrote:
>> To make each percpu area allocated from its local numa node. Without this
>> patch, all percpu areas will be allocated from the node which cpu0 belongs
>> to.
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>> arch/arm64/Kconfig | 8 ++++++++
>> arch/arm64/mm/numa.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 63 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index bc3f00f..2815af6 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -603,6 +603,14 @@ config USE_PERCPU_NUMA_NODE_ID
>> def_bool y
>> depends on NUMA
>>
>> +config HAVE_SETUP_PER_CPU_AREA
>> + def_bool y
>> + depends on NUMA
>> +
>> +config NEED_PER_CPU_EMBED_FIRST_CHUNK
>> + def_bool y
>> + depends on NUMA
>
> Why do we need this? Is it purely about using block mappings for the
> pcpu area?
Without NEED_PER_CPU_EMBED_FIRST_CHUNK, Link error will be reported.

#if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
!defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
#define BUILD_EMBED_FIRST_CHUNK
#endif

#if defined(BUILD_EMBED_FIRST_CHUNK)
//pcpu_embed_first_chunk definition
#endif

setup_per_cpu_areas -->pcpu_embed_first_chunk

>
>> source kernel/Kconfig.preempt
>> source kernel/Kconfig.hz
>>
>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
>> index 7b73808..5e44ad1 100644
>> --- a/arch/arm64/mm/numa.c
>> +++ b/arch/arm64/mm/numa.c
>> @@ -26,6 +26,7 @@
>> #include <linux/of.h>
>>
>> #include <asm/acpi.h>
>> +#include <asm/sections.h>
>>
>> struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
>> EXPORT_SYMBOL(node_data);
>> @@ -131,6 +132,60 @@ void __init early_map_cpu_to_node(unsigned int cpu, int nid)
>> cpu_to_node_map[cpu] = nid;
>> }
>>
>> +#ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
>> +unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
>> +EXPORT_SYMBOL(__per_cpu_offset);
>> +
>> +static int __init early_cpu_to_node(int cpu)
>> +{
>> + return cpu_to_node_map[cpu];
>> +}
>> +
>> +static int __init pcpu_cpu_distance(unsigned int from, unsigned int to)
>> +{
>> + if (early_cpu_to_node(from) == early_cpu_to_node(to))
>> + return LOCAL_DISTANCE;
>> + else
>> + return REMOTE_DISTANCE;
>> +}
>
> Is it too early to use __node_distance here?
Good, we can directly use node_distance, thanks.

>
>> +static void * __init pcpu_fc_alloc(unsigned int cpu, size_t size,
>> + size_t align)
>> +{
>> + int nid = early_cpu_to_node(cpu);
>> +
>> + return memblock_virt_alloc_try_nid(size, align,
>> + __pa(MAX_DMA_ADDRESS), MEMBLOCK_ALLOC_ACCESSIBLE, nid);
>> +}
>> +
>> +static void __init pcpu_fc_free(void *ptr, size_t size)
>> +{
>> + memblock_free_early(__pa(ptr), size);
>> +}
>> +
>> +void __init setup_per_cpu_areas(void)
>> +{
>> + unsigned long delta;
>> + unsigned int cpu;
>> + int rc;
>> +
>> + /*
>> + * Always reserve area for module percpu variables. That's
>> + * what the legacy allocator did.
>> + */
>> + rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
>> + PERCPU_DYNAMIC_RESERVE, PAGE_SIZE,
>> + pcpu_cpu_distance,
>> + pcpu_fc_alloc, pcpu_fc_free);
>> + if (rc < 0)
>> + panic("Failed to initialize percpu areas.");
>> +
>> + delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
>> + for_each_possible_cpu(cpu)
>> + __per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
>> +}
>> +#endif
>
> It's a pity that this is practically identical to PowerPC. Ideally, there
> would be definitions of this initialisation gunk in the core code that
> could be reused across architectures.
But these are different from other ARCHs, except PPC.

I originally want to put it into driver/of/of_numa.c, but now the ACPI NUMA is
coming up, so I don't known where.

>
> Will
>
> .
>