sparse irq_desc[] array: core kernel and x86 changes
Impact: new feature
Problem on distro kernels: irq_desc[NR_IRQS] takes megabytes of RAM with
NR_CPUS set to large values. The goal is to be able to scale up to much
larger NR_IRQS value without impacting the (important) common case.
To solve this, we generalize irq_desc[NR_IRQS] to an (optional) array of
irq_desc pointers.
When CONFIG_SPARSE_IRQ=y is used, we use kzalloc_node to get irq_desc,
this also makes the IRQ descriptors NUMA-local (to the site that calls
request_irq()).
This gets rid of the irq_cfg[] static array on x86 as well: irq_cfg now
uses desc->chip_data for x86 to store irq_cfg.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index c815b42..96ca203 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -15,9 +15,16 @@
#include <linux/random.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
+#include <linux/rculist.h>
+#include <linux/hash.h>
#include "internals.h"
+/*
+ * lockdep: we want to handle all irq_desc locks as a single lock-class:
+ */
+static struct lock_class_key irq_desc_lock_class;
+
/**
* handle_bad_irq - handle spurious and unhandled irqs
* @irq: the interrupt number
@@ -49,6 +56,155 @@
int nr_irqs = NR_IRQS;
EXPORT_SYMBOL_GPL(nr_irqs);
+void __init __attribute__((weak)) arch_early_irq_init(void)
+{
+}
+
+#ifdef CONFIG_SPARSE_IRQ
+static struct irq_desc irq_desc_init = {
+ .irq = -1,
+ .status = IRQ_DISABLED,
+ .chip = &no_irq_chip,
+ .handle_irq = handle_bad_irq,
+ .depth = 1,
+ .lock = __SPIN_LOCK_UNLOCKED(irq_desc_init.lock),
+#ifdef CONFIG_SMP
+ .affinity = CPU_MASK_ALL
+#endif
+};
+
+static void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr)
+{
+ unsigned long bytes;
+ char *ptr;
+ int node;
+
+ /* Compute how many bytes we need per irq and allocate them */
+ bytes = nr * sizeof(unsigned int);
+
+ node = cpu_to_node(cpu);
+ ptr = kzalloc_node(bytes, GFP_ATOMIC, node);
+ printk(KERN_DEBUG " alloc kstat_irqs on cpu %d node %d\n", cpu, node);
+
+ if (ptr)
+ desc->kstat_irqs = (unsigned int *)ptr;
+}
+
+void __attribute__((weak)) arch_init_chip_data(struct irq_desc *desc, int cpu)
+{
+}
+
+static void init_one_irq_desc(int irq, struct irq_desc *desc, int cpu)
+{
+ memcpy(desc, &irq_desc_init, sizeof(struct irq_desc));
+ desc->irq = irq;
+#ifdef CONFIG_SMP
+ desc->cpu = cpu;
+#endif
+ lockdep_set_class(&desc->lock, &irq_desc_lock_class);
+ init_kstat_irqs(desc, cpu, nr_cpu_ids);
+ if (!desc->kstat_irqs) {
+ printk(KERN_ERR "can not alloc kstat_irqs\n");
+ BUG_ON(1);
+ }
+ arch_init_chip_data(desc, cpu);
+}
+
+/*
+ * Protect the sparse_irqs:
+ */
+static DEFINE_SPINLOCK(sparse_irq_lock);
+
+struct irq_desc *irq_desc_ptrs[NR_IRQS] __read_mostly;
+
+static struct irq_desc irq_desc_legacy[16] __cacheline_aligned_in_smp = {
+ [0 ... 15] = {
+ .irq = -1,
+ .status = IRQ_DISABLED,
+ .chip = &no_irq_chip,
+ .handle_irq = handle_bad_irq,
+ .depth = 1,
+ .lock = __SPIN_LOCK_UNLOCKED(irq_desc_init.lock),
+#ifdef CONFIG_SMP
+ .affinity = CPU_MASK_ALL
+#endif
+ }
+};
+
+/* FIXME: use bootmem alloc ...*/
+static unsigned int kstat_irqs_legacy[16][NR_CPUS];
+
+void __init early_irq_init(void)
+{
+ struct irq_desc *desc;
+ int legacy_count;
+ int i;
+
+ desc = irq_desc_legacy;
+ legacy_count = ARRAY_SIZE(irq_desc_legacy);
+
+ for (i = 0; i < legacy_count; i++) {
+ desc[i].irq = i;
+ desc[i].kstat_irqs = kstat_irqs_legacy[i];
+
+ irq_desc_ptrs[i] = desc + i;
+ }
+
+ for (i = legacy_count; i < NR_IRQS; i++)
+ irq_desc_ptrs[i] = NULL;
+
+ arch_early_irq_init();
+}
+
+struct irq_desc *irq_to_desc(unsigned int irq)
+{
+ return (irq < NR_IRQS) ? irq_desc_ptrs[irq] : NULL;
+}
+
+struct irq_desc *irq_to_desc_alloc_cpu(unsigned int irq, int cpu)
+{
+ struct irq_desc *desc;
+ unsigned long flags;
+ int node;
+
+ if (irq >= NR_IRQS) {
+ printk(KERN_WARNING "irq >= NR_IRQS in irq_to_desc_alloc: %d %d\n",
+ irq, NR_IRQS);
+ WARN_ON(1);
+ return NULL;
+ }
+
+ desc = irq_desc_ptrs[irq];
+ if (desc)
+ return desc;
+
+ spin_lock_irqsave(&sparse_irq_lock, flags);
+
+ /* We have to check it to avoid races with another CPU */
+ desc = irq_desc_ptrs[irq];
+ if (desc)
+ goto out_unlock;
+
+ node = cpu_to_node(cpu);
+ desc = kzalloc_node(sizeof(*desc), GFP_ATOMIC, node);
+ printk(KERN_DEBUG " alloc irq_desc for %d on cpu %d node %d\n",
+ irq, cpu, node);
+ if (!desc) {
+ printk(KERN_ERR "can not alloc irq_desc\n");
+ BUG_ON(1);
+ }
+ init_one_irq_desc(irq, desc, cpu);
+
+ irq_desc_ptrs[irq] = desc;
+
+out_unlock:
+ spin_unlock_irqrestore(&sparse_irq_lock, flags);
+
+ return desc;
+}
+
+#else
+
struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = {
[0 ... NR_IRQS-1] = {
.status = IRQ_DISABLED,
@@ -62,6 +218,8 @@
}
};
+#endif
+
/*
* What should we do if we get a hw irq event on an illegal vector?
* Each architecture has to answer this themself.
@@ -261,17 +419,28 @@
#ifdef CONFIG_TRACE_IRQFLAGS
-/*
- * lockdep: we want to handle all irq_desc locks as a single lock-class:
- */
-static struct lock_class_key irq_desc_lock_class;
-
void early_init_irq_lock_class(void)
{
+#ifndef CONFIG_SPARSE_IRQ
struct irq_desc *desc;
int i;
- for_each_irq_desc(i, desc)
+ for_each_irq_desc(i, desc) {
+ if (!desc)
+ continue;
+
lockdep_set_class(&desc->lock, &irq_desc_lock_class);
+ }
+#endif
}
#endif
+
+#ifdef CONFIG_SPARSE_IRQ
+unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+ return desc->kstat_irqs[cpu];
+}
+#endif
+EXPORT_SYMBOL(kstat_irqs_cpu);
+
