Re: SMP P4 APIC/interrupt balancing

Ingo Molnar (mingo@elte.hu)
Wed, 17 Apr 2002 19:07:41 +0200 (CEST)


On Wed, 17 Apr 2002, James Bourne wrote:

> Where would I find this separate patch? Is there something I could do
> some testing on?

the timer irq inbalance problem should be solved by the attached patch.

Ingo

diff -up --recursive --new-file linux-2.4.18.macro/arch/i386/kernel/io_apic.c linux-2.4.18/arch/i386/kernel/io_apic.c
--- linux-2.4.18.macro/arch/i386/kernel/io_apic.c Fri Nov 23 15:32:04 2001
+++ linux-2.4.18/arch/i386/kernel/io_apic.c Fri Mar 1 14:58:20 2002
@@ -67,7 +67,7 @@ static struct irq_pin_list {
* shared ISA-space IRQs, so we have to support them. We are super
* fast in the common case, and fast for shared ISA-space IRQs.
*/
-static void add_pin_to_irq(unsigned int irq, int apic, int pin)
+static void __init add_pin_to_irq(unsigned int irq, int apic, int pin)
{
static int first_free_entry = NR_IRQS;
struct irq_pin_list *entry = irq_2_pin + irq;
@@ -85,6 +85,26 @@ static void add_pin_to_irq(unsigned int
entry->pin = pin;
}

+/*
+ * Reroute an IRQ to a different pin.
+ */
+static void __init replace_pin_at_irq(unsigned int irq,
+ int oldapic, int oldpin,
+ int newapic, int newpin)
+{
+ struct irq_pin_list *entry = irq_2_pin + irq;
+
+ while (1) {
+ if (entry->apic == oldapic && entry->pin == oldpin) {
+ entry->apic = newapic;
+ entry->pin = newpin;
+ }
+ if (!entry->next)
+ break;
+ entry = irq_2_pin + entry->next;
+ }
+}
+
#define __DO_ACTION(R, ACTION, FINAL) \
\
{ \
@@ -1533,6 +1553,10 @@ static inline void check_timer(void)
setup_ExtINT_IRQ0_pin(pin2, vector);
if (timer_irq_works()) {
printk("works.\n");
+ if (pin1 != -1)
+ replace_pin_at_irq(0, 0, pin1, 0, pin2);
+ else
+ add_pin_to_irq(0, 0, pin2);
if (nmi_watchdog == NMI_IO_APIC) {
setup_nmi();
check_nmi_watchdog();

-
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