/* cpumap.c: used for optimizing CPU assignment
*
* Copyright (C) 2009 Hong H. Pham <hong.pham@windriver.com>
*/
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <asm/cpudata.h>
#include "cpumap.h"
enum {
CPUINFO_LVL_ROOT = 0,
CPUINFO_LVL_NODE,
CPUINFO_LVL_CORE,
CPUINFO_LVL_PROC,
CPUINFO_LVL_MAX,
};
enum {
ROVER_NO_OP = 0,
/* Increment rover every time level is visited */
ROVER_INC_ON_VISIT = 1 << 0,
/* Increment parent's rover every time rover wraps around */
ROVER_INC_PARENT_ON_LOOP = 1 << 1,
};
struct cpuinfo_node {
int id;
int level;
int num_cpus; /* Number of CPUs in this hierarchy */
int parent_index;
int child_start; /* Array index of the first child node */
int child_end; /* Array index of the last child node */
int rover; /* Child node iterator */
};
struct cpuinfo_level {
int start_index; /* Index of first node of a level in a cpuinfo tree */
int end_index; /* Index of last node of a level in a cpuinfo tree */
int num_nodes; /* Number of nodes in a level in a cpuinfo tree */
};
struct cpuinfo_tree {
int total_nodes;
/* Offsets into nodes[] for each level of the tree */
struct cpuinfo_level level[CPUINFO_LVL_MAX];
struct cpuinfo_node nodes[0];
};
static struct cpuinfo_tree *cpuinfo_tree;
static u16 cpu_distribution_map[NR_CPUS];
static DEFINE_SPINLOCK(cpu_map_lock);
/* Niagara optimized cpuinfo tree traversal. */
static const int niagara_iterate_method[] = {
[CPUINFO_LVL_ROOT] = ROVER_NO_OP,
/* Strands (or virtual CPUs) within a core may not run concurrently
* on the Niagara, as instruction pipeline(s) are shared. Distribute
* work to strands in different cores first for better concurrency.
* Go to next NUMA node when all cores are used.
*/
[CPUINFO_LVL_NODE] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP,
/* Strands are grouped together by proc_id in cpuinfo_sparc, i.e.
* a proc_id represents an instruction pipeline. Distribute work to
* strands in different proc_id groups if the core has multiple
* instruction pipelines (e.g. the Niagara 2/2+ has two).
*/
[CPUINFO_LVL_CORE] = ROVER_INC_ON_VISIT,
/* Pick the next strand in the proc_id group. */
[CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT,
};
/* Generic cpuinfo tree traversal. Distribute work round robin across NUMA
* nodes.
*/
static const int generic_iterate_method[] = {
[CPUINFO_LVL_ROOT] = ROVER_INC_ON_VISIT,
[CPUINFO_LVL_NODE] = ROVER_NO_OP,
[CPUINFO_LVL_CORE] = ROVER_INC_PARENT_ON_LOOP,
[CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP,
};
static int cpuinfo_id(int cpu, int level)
{
int id;
switch (level) {
case CPUINFO_LVL_ROOT:
id = 0;
break;
case CPUINFO_LVL_NODE:
id = cpu_to_node(cpu);
break;
case CPUINFO_LVL_CORE:
id = cpu_data(cpu).core_id;
break;
case CPUINFO_LVL_PROC:
id = cpu_data(cpu).proc_id;
break;
default:
id = -EINVAL;
}
return id;
}
/*
* Enumerate the CPU information in __cpu_data to determine the start index,
* end index, and number of nodes for each level in the cpuinfo tree. The
* total number of cpuinfo nodes required to build the tree is returned.
*/
static int enumerate_cpuinfo_nodes(struct cpuinfo_level *tree_level)
{
int prev_id[CPUINFO_LVL_MAX];
int i, n, num_nodes;
for (i = CPUINFO_LVL_ROOT; i < CPUINFO_LVL_MAX; i++) {
struct cpuinfo_level *lv = &tree_level[i];
prev_id[i] = -1;
lv->start_index = lv->end_index = lv->num_nodes = 0;
}
num_nodes = 1; /* Include the root node */
for (i = 0; i < num_possible_cpus(); i++) {
if (!cpu_online(i))
continue;
n = cpuinfo_id(i, CPUINFO_LVL_NODE);
if (n > prev_id[CPUINFO_LVL_NODE]) {
tree_level[CPUINFO_LVL_NODE].num_nodes++;
prev_id[CPUINFO_LVL_NODE] = n;
num_nodes++;
}
n = cpuinfo_id(i, CPUINFO_LVL_CORE);
if (n > prev_id[CPUINFO_LVL_CORE]) {
tree_level[CPUINFO_LVL_CORE].num_nodes++;
prev_id[CPUINFO_LVL_CORE] = n;
num_nodes++;
}
n = cpuinfo_id(i, CPUINFO_LVL_PROC);
if (n > prev_id[CPUINFO_LVL_PROC]) {
tree_level[CPUINFO_LVL_PROC].num_nodes++;
prev_id[CPUINFO_LVL_PROC] = n;
num_nodes++;
}
}
tree_level[CPUINFO_LVL_ROOT].num_nodes = 1;
n = tree_level[CPUINFO_LVL_NODE].num_nodes;
tree_level[CPUINFO_LVL_NODE].start_index = 1;
tree_level[CPUINFO_LVL_NODE].end_index = n;
n++;
tree_level[CPUINFO_LVL_CORE].start_index = n;
n += tree_level[CPUINFO_LVL_CORE].num_nodes;
tree_level[CPUINFO_LVL_CORE].end_index = n - 1;
tree_level[CPUINFO_LVL_PROC].start_index = n;
n += tree_level[CPUINFO_LVL_PROC].num_nodes;
tree_level[CPUINFO_LVL_PROC].end_index = n - 1;
return num_nodes;
}
/* Build a tree representation of the CPU hierarchy using the per CPU
* information in __cpu_data. Entries in __cpu_data[0..NR_CPUS] are
* assumed to be sorted in ascending order based on node, core_id, and
* proc_id (in order of significance).
*/
static struct cpuinfo_tree *build_cpuinfo_tree(void)
{
struct cpuinfo_tree *new_tree;
struct cpuinfo_node *node;
struct cpuinfo_level tmp_level[CPUINFO_LVL_MAX];
int num_cpus[CPUINFO_LVL_MAX];
int level_rover[CPUINFO_LVL_MAX];
int prev_id[CPUINFO_LVL_MAX];
int n, id, cpu, prev_cpu, last_cpu, level;
n = enumerate_cpuinfo_nodes(tmp_level);
new_tree = kzalloc(sizeof(struct cpuinfo_tree) +
(sizeof(struct cpuinfo_node) * n), GFP_ATOMIC);
if (!new_tree)
return NULL;
new_tree->total_nodes = n;
memcpy(&new_tree->level, tmp_level, sizeof(tmp_level));
prev_cpu = cpu = cpumask_first(cpu_online_mask);
/* Initialize all levels in the tree with the first CPU */
for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT; level--) {
n = new_tree->level[level].start_index;
level_rover[level] = n;
node = &new_tree->nodes[n];
id = cpuinfo_id(cpu, level);
if (unlikely(id < 0)) {
kfree(new_tree);
return NULL;
}
node->id = id;
node->level = level;
node->num_cpus = 1;
node->parent_index = (level > CPUINFO_LVL_ROOT)
? new_tree->level[level - 1].start_index : -1;
node->child_start = node->child_end = node->rover =
(level == CPUINFO_LVL_PROC)
? cpu : new_tree->level[level + 1].start_index;
prev_id[level] = node->id;
num_cpus[level] = 1;
}
for (last_cpu = (num_possible_cpus() - 1); last_cpu >= 0; last_cpu--) {
if (cpu_online(last_cpu))
break;
}
while (++cpu <= last_cpu) {
if (!cpu_online(cpu))
continue;
for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT;
level--) {
id = cpuinfo_id(cpu, level);
if (unlikely(id < 0)) {
kfree(new_tree);
return NULL;
}
if ((id != prev_id[level]) || (cpu == last_cpu)) {
prev_id[level] = id;
node = &new_tree->nodes[level_rover[level]];
node->num_cpus = num_cpus[level];
num_cpus[level] = 1;
if (cpu == last_cpu)
node->num_cpus++;
/* Connect tree node to parent */
if (level == CPUINFO_LVL_ROOT)
node->parent_index = -1;
else
node->parent_index =
level_rover[level - 1];
if (level == CPUINFO_LVL_PROC) {
node->child_end =
(cpu == last_cpu) ? cpu : prev_cpu;
} else {
node->child_end =
level_rover[level + 1] - 1;
}
/* Initialize the next node in the same level */
n = ++level_rover[level];
if (n <= new_tree->level[level].end_index) {
node = &new_tree->nodes[n];
node->id = id;
node->level = level;
/* Connect node to child */
node->child_start = node->child_end =
node->rover =
(level == CPUINFO_LVL_PROC)
? cpu : level_rover[level + 1];
}
} else
num_cpus[level]++;
}
prev_cpu = cpu;
}
return new_tree;
}
static void increment_rover(struct cpuinfo_tree *t, int node_index,
int root_index, const int *rover_inc_table)
{
struct cpuinfo_node *node = &t->nodes[node_index];
int top_level, level;
top_level = t->nodes[root_index].level;
for (level = node->level; level >= top_level; level--) {
node->rover++;
if (node->rover <= node->child_end)
return;
node->rover = node->child_start;
/* If parent's rover does not need to be adjusted, stop here. */
if ((level == top_level) ||
!(rover_inc_table[level] & ROVER_INC_PARENT_ON_LOOP))
return;
node = &t->nodes[node->parent_index];
}
}
static int iterate_cpu(struct cpuinfo_tree *t, unsigned int root_index)
{
const int *rover_inc_table;
int level, new_index, index = root_index;
switch (sun4v_chip_type) {
case SUN4V_CHIP_NIAGARA1:
case SUN4V_CHIP_NIAGARA2:
case SUN4V_CHIP_NIAGARA3:
case SUN4V_CHIP_NIAGARA4:
case SUN4V_CHIP_NIAGARA5:
case SUN4V_CHIP_SPARC64X:
rover_inc_table = niagara_iterate_method;
break;
default:
rover_inc_table = generic_iterate_method;
}
for (level = t->nodes[root_index].level; level < CPUINFO_LVL_MAX;
level++) {
new_index = t->nodes[index].rover;
if (rover_inc_table[level] & ROVER_INC_ON_VISIT)
increment_rover(t, index, root_index, rover_inc_table);
index = new_index;
}
return index;
}
static void _cpu_map_rebuild(void)
{
int i;
if (cpuinfo_tree) {
kfree(cpuinfo_tree);
cpuinfo_tree = NULL;
}
cpuinfo_tree = build_cpuinfo_tree();
if (!cpuinfo_tree)
return;
/* Build CPU distribution map that spans all online CPUs. No need
* to check if the CPU is online, as that is done when the cpuinfo
* tree is being built.
*/
for (i = 0; i < cpuinfo_tree->nodes[0].num_cpus; i++)
cpu_distribution_map[i] = iterate_cpu(cpuinfo_tree, 0);
}
/* Fallback if the cpuinfo tree could not be built. CPU mapping is linear
* round robin.
*/
static int simple_map_to_cpu(unsigned int index)
{
int i, end, cpu_rover;
cpu_rover = 0;
end = index % num_online_cpus();
for (i = 0; i < num_possible_cpus(); i++) {
if (cpu_online(cpu_rover)) {
if (cpu_rover >= end)
return cpu_rover;
cpu_rover++;
}
}
/* Impossible, since num_online_cpus() <= num_possible_cpus() */
return cpumask_first(cpu_online_mask);
}
static int _map_to_cpu(unsigned int index)
{
struct cpuinfo_node *root_node;
if (unlikely(!cpuinfo_tree)) {
_cpu_map_rebuild();
if (!cpuinfo_tree)
return simple_map_to_cpu(index);
}
root_node = &cpuinfo_tree->nodes[0];
#ifdef CONFIG_HOTPLUG_CPU
if (unlikely(root_node->num_cpus != num_online_cpus())) {
_cpu_map_rebuild();
if (!cpuinfo_tree)
return simple_map_to_cpu(index);
}
#endif
return cpu_distribution_map[index % root_node->num_cpus];
}
int map_to_cpu(unsigned int index)
{
int mapped_cpu;
unsigned long flag;
spin_lock_irqsave(&cpu_map_lock, flag);
mapped_cpu = _map_to_cpu(index);
#ifdef CONFIG_HOTPLUG_CPU
while (unlikely(!cpu_online(mapped_cpu)))
mapped_cpu = _map_to_cpu(index);
#endif
spin_unlock_irqrestore(&cpu_map_lock, flag);
return mapped_cpu;
}
EXPORT_SYMBOL(map_to_cpu);
void cpu_map_rebuild(void)
{
unsigned long flag;
spin_lock_irqsave(&cpu_map_lock, flag);
_cpu_map_rebuild();
spin_unlock_irqrestore(&cpu_map_lock, flag);
}
