Commit 05b3cbd8 authored by Ravikiran Thirumalai's avatar Ravikiran Thirumalai Committed by Linus Torvalds
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[PATCH] x86_64: Early initialization of cpu_to_node

Patch enables early intialization of cpu_to_node.
apicid_to_node is built by reading the SRAT table, from acpi_numa_init with
ACPI_NUMA and k8_scan_nodes with K8_NUMA.
x86_cpu_to_apicid is built by parsing the ACPI MADT table, from acpi_boot_init.
We combine these two tables and setup cpu_to_node.

Early intialization helps the static per_cpu_areas in getting pages from
correct node.

Change since last release:
Do not initialize early init_cpu_to_node for faking node cases.

Patch tested on TYAN dual core 4P board with K8 only, ACPI_NUMA.
Tested on EM64T NUMA. Also tested with numa=off, numa=fake, and  running
a kernel compiled with NUMA on a regular EM64 2 way SMP.

Signed-off-by: default avatarAlok N Kataria <>
Signed-off-by: default avatarRavikiran Thirumalai <>
Signed-off-by: default avatarShai Fultheim <>
Signed-off-by: default avatarAndi Kleen <>
Signed-off-by: default avatarLinus Torvalds <>
parent 0b91317e
......@@ -713,6 +713,8 @@ void __init setup_arch(char **cmdline_p)
* get boot-time SMP configuration:
......@@ -330,6 +330,31 @@ __init int numa_setup(char *opt)
return 1;
* Setup early cpu_to_node.
* Populate cpu_to_node[] only if x86_cpu_to_apicid[],
* and apicid_to_node[] tables have valid entries for a CPU.
* This means we skip cpu_to_node[] initialisation for NUMA
* emulation and faking node case (when running a kernel compiled
* for NUMA on a non NUMA box), which is OK as cpu_to_node[]
* is already initialized in a round robin manner at numa_init_array,
* prior to this call, and this initialization is good enough
* for the fake NUMA cases.
void __init init_cpu_to_node(void)
int i;
for (i = 0; i < NR_CPUS; i++) {
u8 apicid = x86_cpu_to_apicid[i];
if (apicid == BAD_APICID)
if (apicid_to_node[apicid] == NUMA_NO_NODE)
cpu_to_node[i] = apicid_to_node[apicid];
......@@ -20,6 +20,11 @@ extern int numa_off;
extern void numa_set_node(int cpu, int node);
extern unsigned char apicid_to_node[256];
extern void __init init_cpu_to_node(void);
#define init_cpu_to_node() do {} while (0)
#define NUMA_NO_NODE 0xff
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