[PATCH/RFC 4/6] numa: Introduce numa_mem_id()- effective local memory node id

Lee Schermerhorn
2009-11-13T21:13:05Z

Against: 2.6.32-rc5-mmotm-091101-1001

Introduce numa_mem_id(), based on generic percpu variable infrastructure
to track "nearest node with memory" for archs that support memoryless
nodes.

Define API in <linux/topology.h> when CONFIG_HAVE_MEMORYLESS_NODES
defined, else stubs. Architectures will define HAVE_MEMORYLESS_NODES
if/when they support them.

Archs can override definitions of:

numa_mem_id() - returns node number of "local memory" node
set_numa_mem() - initialize [this cpus'] per cpu variable 'numa_mem'
cpu_to_mem() - return numa_mem for specified cpu; may be used as lvalue

Generic initialization of 'numa_mem' occurs in __build_all_zonelists().
This will initialize the boot cpu at boot time, and all cpus on change of
numa_zonelist_order, or when node or memory hot-plug requires zonelist rebuild.
Archs that support memoryless nodes will need to initialize 'numa_mem' for
secondary cpus as they're brought on-line.

Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>

V2: + split this out of Christoph's incomplete "starter patch"
+ flesh out the definition

---

include/linux/mmzone.h | 6 ++++++
include/linux/topology.h | 24 ++++++++++++++++++++++++
mm/page_alloc.c | 35 +++++++++++++++++++++++++++++++++++
mm/percpu.c | 5 +++++
4 files changed, 70 insertions(+)

Index: linux-2.6.32-rc5-mmotm-091101-1001/include/linux/topology.h
===================================================================
--- linux-2.6.32-rc5-mmotm-091101-1001.orig/include/linux/topology.h
+++ linux-2.6.32-rc5-mmotm-091101-1001/include/linux/topology.h
@@ -232,6 +232,30 @@ DECLARE_PER_CPU(int, numa_node);

#endif /* [!]CONFIG_USE_PERCPU_NUMA_NODE_ID */

+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+
+DECLARE_PER_CPU(int, numa_mem);
+
+#ifndef set_numa_mem
+#define set_numa_mem(__node) percpu_write(numa_mem, __node)
+#endif
+
+#else /* !CONFIG_HAVE_MEMORYLESS_NODES */
+
+#define numa_mem numa_node
+static inline void set_numa_mem(int node) {}
+
+#endif /* [!]CONFIG_HAVE_MEMORYLESS_NODES */
+
+#ifndef numa_mem_id
+/* Returns the number of the nearest Node with memory */
+#define numa_mem_id() __this_cpu_read(numa_mem)
+#endif
+
+#ifndef cpu_to_mem
+#define cpu_to_mem(__cpu) per_cpu(numa_mem, (__cpu))
+#endif
+
#ifndef topology_physical_package_id
#define topology_physical_package_id(cpu) ((void)(cpu), -1)
#endif
Index: linux-2.6.32-rc5-mmotm-091101-1001/mm/percpu.c
===================================================================
--- linux-2.6.32-rc5-mmotm-091101-1001.orig/mm/percpu.c
+++ linux-2.6.32-rc5-mmotm-091101-1001/mm/percpu.c
@@ -2078,3 +2078,8 @@ DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
#endif

+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+DEFINE_PER_CPU(int, numa_mem); /* Kernel "local memory" node */
+EXPORT_PER_CPU_SYMBOL(numa_mem);
+#endif
+
Index: linux-2.6.32-rc5-mmotm-091101-1001/mm/page_alloc.c
===================================================================
--- linux-2.6.32-rc5-mmotm-091101-1001.orig/mm/page_alloc.c
+++ linux-2.6.32-rc5-mmotm-091101-1001/mm/page_alloc.c
@@ -2688,6 +2688,24 @@ static void build_zonelist_cache(pg_data
zlc->z_to_n[z - zonelist->_zonerefs] = zonelist_node_idx(z);
}

+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+/*
+ * Return node id of node used for "local" allocations.
+ * I.e., first node id of first zone in arg node's generic zonelist.
+ * Used for initializing percpu 'numa_mem', which is used primarily
+ * for kernel allocations, so use GFP_KERNEL flags to locate zonelist.
+ */
+int local_memory_node(int node)
+{
+ struct zone *zone;
+
+ (void)first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
+ gfp_zone(GFP_KERNEL),
+ NULL,
+ &zone);
+ return zone->node;
+}
+#endif

#else /* CONFIG_NUMA */

@@ -2754,6 +2772,23 @@ static int __build_all_zonelists(void *d
build_zonelists(pgdat);
build_zonelist_cache(pgdat);
}
+
+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+ {
+ /*
+ * We now know the "local memory node" for each node--
+ * i.e., the node of the first zone in the generic zonelist.
+ * Set up numa_mem percpu variable for on-line cpus. During
+ * boot, only the boot cpu should be on-line; we'll init the
+ * secondary cpus' numa_mem as they come on-line. During
+ * node/memory hotplug, we'll fixup all cpus.
+ */
+ int cpu;
+ for_each_online_cpu(cpu) {
+ cpu_to_mem(cpu) = local_memory_node(cpu_to_node(cpu));
+ }
+ }
+#endif
return 0;
}

Index: linux-2.6.32-rc5-mmotm-091101-1001/include/linux/mmzone.h
===================================================================
--- linux-2.6.32-rc5-mmotm-091101-1001.orig/include/linux/mmzone.h
+++ linux-2.6.32-rc5-mmotm-091101-1001/include/linux/mmzone.h
@@ -672,6 +672,12 @@ void memory_present(int nid, unsigned lo
static inline void memory_present(int nid, unsigned long start, unsigned long end) {}
#endif

+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+int local_memory_node(int node_id);
+#else
+static inline int local_memory_node(int node_id) { return node_id; };
+#endif
+
#ifdef CONFIG_NEED_NODE_MEMMAP_SIZE
unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
#endif