On 2016/8/26 21:28, Will Deacon wrote:

On Wed, Aug 24, 2016 at 03:44:48PM +0800, Zhen Lei wrote:

quoted

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 <redacted>
---
 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

quoted

 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.

quoted

+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

.