sparc64: fix and optimize irq distribution

irq_choose_cpu() should compare the affinity mask against cpu_online_map
rather than CPU_MASK_ALL, since irq_select_affinity() sets the interrupt's
affinity mask to cpu_online_map "and" CPU_MASK_ALL (which ends up being
just cpu_online_map).  The mask comparison in irq_choose_cpu() will always
fail since the two masks are not the same.  So the CPU chosen is the first CPU
in the intersection of cpu_online_map and CPU_MASK_ALL, which is always CPU0.
That means all interrupts are reassigned to CPU0...

Distributing interrupts to CPUs in a linearly increasing round robin fashion
is not optimal for the UltraSPARC T1/T2.  Also, the irq_rover in
irq_choose_cpu() causes an interrupt to be assigned to a different
processor each time the interrupt is allocated and released.  This may lead
to an unbalanced distribution over time.

A static mapping of interrupts to processors is done to optimize and balance
interrupt distribution.  For the T1/T2, interrupts are spread to different
cores first, and then to strands within a core.

The following is some benchmarks showing the effects of interrupt
distribution on a T2.  The test was done with iperf using a pair of T5220
boxes, each with a 10GBe NIU (XAUI) connected back to back.

  TCP     | Stock       Linear RR IRQ  Optimized IRQ
  Streams | 2.6.30-rc5  Distribution   Distribution
          | GBits/sec   GBits/sec      GBits/sec
  --------+-----------------------------------------
    1       0.839       0.862          0.868
    8       1.16        4.96           5.88
   16       1.15        6.40           8.04
  100       1.09        7.28           8.68

Signed-off-by: Hong H. Pham <hong.pham@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 456 insertions, 25 deletions

diff --git a/arch/sparc/kernel/Makefile b/arch/sparc/kernel/Makefile
index 54742e58831..47029c66b17 100644
--- a/arch/sparc/kernel/Makefile
+++ b/arch/sparc/kernel/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_SPARC64)   += sstate.o
 obj-$(CONFIG_SPARC64)   += mdesc.o
 obj-$(CONFIG_SPARC64)   += pcr.o
 obj-$(CONFIG_SPARC64)   += nmi.o
+obj-$(CONFIG_SPARC64_SMP) += cpumap.o
 
 # sparc32 do not use GENERIC_HARDIRQS but uses the generic devres implementation
 obj-$(CONFIG_SPARC32)     += devres.o
diff --git a/arch/sparc/kernel/cpumap.c b/arch/sparc/kernel/cpumap.c
new file mode 100644
index 00000000000..7430ed080b2
--- /dev/null
+++ b/arch/sparc/kernel/cpumap.c
@@ -0,0 +1,431 @@
+/* cpumap.c: used for optimizing CPU assignment
+ *
+ * Copyright (C) 2009 Hong H. Pham <hong.pham@windriver.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.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 = first_cpu(cpu_online_map);
+
+        /* 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:
+                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 first_cpu(cpu_online_map);
+}
+
+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);
+}
diff --git a/arch/sparc/kernel/cpumap.h b/arch/sparc/kernel/cpumap.h
new file mode 100644
index 00000000000..e639880ab86
--- /dev/null
+++ b/arch/sparc/kernel/cpumap.h
@@ -0,0 +1,16 @@
+#ifndef _CPUMAP_H
+#define _CPUMAP_H
+
+#ifdef CONFIG_SMP
+extern void cpu_map_rebuild(void);
+extern int  map_to_cpu(unsigned int index);
+#define cpu_map_init() cpu_map_rebuild()
+#else
+#define cpu_map_init() do {} while (0)
+static inline int map_to_cpu(unsigned int index)
+{
+        return raw_smp_processor_id();
+}
+#endif
+
+#endif
diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index e5e78f9cfc9..bd075054942 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -45,6 +45,7 @@
 #include <asm/cacheflush.h>
 
 #include "entry.h"
+#include "cpumap.h"
 
 #define NUM_IVECS       (IMAP_INR + 1)
 
@@ -256,35 +257,13 @@ static int irq_choose_cpu(unsigned int virt_irq)
         int cpuid;
 
         cpumask_copy(&mask, irq_desc[virt_irq].affinity);
-        if (cpus_equal(mask, CPU_MASK_ALL)) {
-                static int irq_rover;
-                static DEFINE_SPINLOCK(irq_rover_lock);
-                unsigned long flags;
-
-                /* Round-robin distribution... */
-        do_round_robin:
-                spin_lock_irqsave(&irq_rover_lock, flags);
-
-                while (!cpu_online(irq_rover)) {
-                        if (++irq_rover >= nr_cpu_ids)
-                                irq_rover = 0;
-                }
-                cpuid = irq_rover;
-                do {
-                        if (++irq_rover >= nr_cpu_ids)
-                                irq_rover = 0;
-                } while (!cpu_online(irq_rover));
-
-                spin_unlock_irqrestore(&irq_rover_lock, flags);
+        if (cpus_equal(mask, cpu_online_map)) {
+                cpuid = map_to_cpu(virt_irq);
         } else {
                 cpumask_t tmp;
 
                 cpus_and(tmp, cpu_online_map, mask);
-
-                if (cpus_empty(tmp))
-                        goto do_round_robin;
-
-                cpuid = first_cpu(tmp);
+                cpuid = cpus_empty(tmp) ? map_to_cpu(virt_irq) : first_cpu(tmp);
         }
 
         return cpuid;
diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index 1de47d2169c..cfb3d06058f 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -48,6 +48,8 @@
 #include <asm/ldc.h>
 #include <asm/hypervisor.h>
 
+#include "cpumap.h"
+
 int sparc64_multi_core __read_mostly;
 
 DEFINE_PER_CPU(cpumask_t, cpu_sibling_map) = CPU_MASK_NONE;
@@ -1314,6 +1316,8 @@ int __cpu_disable(void)
         cpu_clear(cpu, cpu_online_map);
         ipi_call_unlock();
 
+        cpu_map_rebuild();
+
         return 0;
 }