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>

2 files changed, 18 insertions, 5 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
    -------------------------------------------------------------------------- */