x86: arch_probe_nr_irqs

Impact: save RAM with large NR_CPUS, get smaller nr_irqs

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Mike Travis <travis@sgi.com>

5 files changed, 26 insertions, 12 deletions

diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 602361ad0e74..a16a2ab2b429 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -115,14 +115,11 @@
 # endif
 #else
 
-/* defined as a macro so nr_irqs = max_nr_irqs(nr_cpu_ids) can be used */
-# define max_nr_irqs(nr_cpus)                           \
-        ((8 * nr_cpus) > (32 * MAX_IO_APICS) ?          \
+# define NR_IRQS                                        \
+        ((8 * NR_CPUS) > (32 * MAX_IO_APICS) ?          \
                 (NR_VECTORS + (8 * NR_CPUS)) :          \
                 (NR_VECTORS + (32 * MAX_IO_APICS)))     \
 
-# define NR_IRQS max_nr_irqs(NR_CPUS)
-
 #endif
 
 #elif defined(CONFIG_X86_VOYAGER)
diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index ae80638012de..157986916cd1 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -3850,6 +3850,22 @@ void __init probe_nr_irqs_gsi(void)
                 nr_irqs_gsi = nr;
 }
 
+#ifdef CONFIG_SPARSE_IRQ
+int __init arch_probe_nr_irqs(void)
+{
+        int nr;
+
+        nr = ((8 * nr_cpu_ids) > (32 * nr_ioapics) ?
+                (NR_VECTORS + (8 * nr_cpu_ids)) :
+                (NR_VECTORS + (32 * nr_ioapics)));
+
+        if (nr < nr_irqs && nr > nr_irqs_gsi)
+                nr_irqs = nr;
+
+        return 0;
+}
+#endif
+
 /* --------------------------------------------------------------------------
                           ACPI-based IOAPIC Configuration
    -------------------------------------------------------------------------- */
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 9127f6b51a39..472f11765f60 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -467,6 +467,7 @@ int show_interrupts(struct seq_file *p, void *v);
 struct irq_desc;
 
 extern int early_irq_init(void);
+extern int arch_probe_nr_irqs(void);
 extern int arch_early_irq_init(void);
 extern int arch_init_chip_data(struct irq_desc *desc, int cpu);
 
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 04d3e46031e5..375d68cd5bf0 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -59,10 +59,6 @@ EXPORT_SYMBOL_GPL(nr_irqs);
 
 #ifdef CONFIG_SPARSE_IRQ
 
-#ifndef max_nr_irqs
-#define max_nr_irqs(nr_cpus)    NR_IRQS
-#endif
-
 static struct irq_desc irq_desc_init = {
         .irq        = -1,
         .status     = IRQ_DISABLED,
@@ -137,9 +133,8 @@ int __init early_irq_init(void)
         int legacy_count;
         int i;
 
-        /* initialize nr_irqs based on nr_cpu_ids */
-        nr_irqs = max_nr_irqs(nr_cpu_ids);
-
+         /* initialize nr_irqs based on nr_cpu_ids */
+        arch_probe_nr_irqs();
         printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d\n", NR_IRQS, nr_irqs);
 
         desc = irq_desc_legacy;
diff --git a/kernel/softirq.c b/kernel/softirq.c
index bdbe9de9cd8d..0365b4899a3d 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -795,6 +795,11 @@ int __init __weak early_irq_init(void)
         return 0;
 }
 
+int __init __weak arch_probe_nr_irqs(void)
+{
+        return 0;
+}
+
 int __init __weak arch_early_irq_init(void)
 {
         return 0;