The following patch extirpates cacheline bouncing due to
apic_timer_irqs[NR_CPUS] array, by placing them in the irq_stat[] cacheline
aligned array for i386, and cpu_pda[] array for x86_64. (irq_stat structure is
moved to cpu_pda in x86_64). apic_timer_irqs get updated at every local apic
timer interrput, causing the cacheline to bounce. I could have used Rusty's
per-cpu area mechanism, but I wouldn't be able to make a patch for 2.4, and
irq_stat seemed like a good place for apic_timer_irqs.
This patch has been tested on a 4 way PIII xeon. I hope I have got the
x86_64 stuff right. The ia64 part is probably dead code lying around to
make irq.c platform independent in the future. Please consider for 2.5.18*
Kiran
diff -ruN -X dontdiff linux-2.5.17/arch/i386/kernel/apic.c apic_timer_irqs/arch/i386/kernel/apic.c
--- linux-2.5.17/arch/i386/kernel/apic.c Tue May 21 10:37:39 2002
+++ apic_timer_irqs/arch/i386/kernel/apic.c Thu May 23 15:59:25 2002
@@ -1063,7 +1063,6 @@
* [ if a single-CPU system runs an SMP kernel then we call the local
* interrupt as well. Thus we cannot inline the local irq ... ]
*/
-unsigned int apic_timer_irqs [NR_CPUS];
void smp_apic_timer_interrupt(struct pt_regs regs)
{
@@ -1072,7 +1071,7 @@
/*
* the NMI deadlock-detector uses this.
*/
- apic_timer_irqs[cpu]++;
+ irq_stat[cpu].apic_timer_irqs++;
/*
* NOTE! We'd better ACK the irq immediately,
diff -ruN -X dontdiff linux-2.5.17/arch/i386/kernel/irq.c apic_timer_irqs/arch/i386/kernel/irq.c
--- linux-2.5.17/arch/i386/kernel/irq.c Tue May 21 10:37:31 2002
+++ apic_timer_irqs/arch/i386/kernel/irq.c Thu May 23 13:00:12 2002
@@ -168,7 +168,8 @@
#if CONFIG_X86_LOCAL_APIC
seq_printf(p, "LOC: ");
for (j = 0; j < smp_num_cpus; j++)
- seq_printf(p, "%10u ", apic_timer_irqs[cpu_logical_map(j)]);
+ seq_printf(p, "%10u ",
+ irq_stat[cpu_logical_map(j)].apic_timer_irqs);
seq_putc(p, '\n');
#endif
seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
diff -ruN -X dontdiff linux-2.5.17/arch/i386/kernel/nmi.c apic_timer_irqs/arch/i386/kernel/nmi.c
--- linux-2.5.17/arch/i386/kernel/nmi.c Tue May 21 10:37:40 2002
+++ apic_timer_irqs/arch/i386/kernel/nmi.c Thu May 23 13:01:07 2002
@@ -344,7 +344,7 @@
*/
int sum, cpu = smp_processor_id();
- sum = apic_timer_irqs[cpu];
+ sum = irq_stat[cpu].apic_timer_irqs;
if (last_irq_sums[cpu] == sum) {
/*
diff -ruN -X dontdiff linux-2.5.17/arch/ia64/kernel/irq.c apic_timer_irqs/arch/ia64/kernel/irq.c
--- linux-2.5.17/arch/ia64/kernel/irq.c Tue May 21 10:37:36 2002
+++ apic_timer_irqs/arch/ia64/kernel/irq.c Thu May 23 16:59:52 2002
@@ -189,7 +189,7 @@
seq_puts(p, "LOC: ");
for (j = 0; j < smp_num_cpus; j++)
seq_printf(p, "%10u ",
- apic_timer_irqs[cpu_logical_map(j)]);
+ irq_stat[cpu_logical_map(j)].apic_timer_irqs);
seq_putc(p, '\n');
#endif
seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
diff -ruN -X dontdiff linux-2.5.17/arch/x86_64/kernel/apic.c apic_timer_irqs/arch/x86_64/kernel/apic.c
--- linux-2.5.17/arch/x86_64/kernel/apic.c Tue May 21 10:37:32 2002
+++ apic_timer_irqs/arch/x86_64/kernel/apic.c Fri May 24 09:57:53 2002
@@ -1044,7 +1044,6 @@
* [ if a single-CPU system runs an SMP kernel then we call the local
* interrupt as well. Thus we cannot inline the local irq ... ]
*/
-unsigned int apic_timer_irqs [NR_CPUS];
void smp_apic_timer_interrupt(struct pt_regs *regs)
{
@@ -1053,7 +1052,7 @@
/*
* the NMI deadlock-detector uses this.
*/
- apic_timer_irqs[cpu]++;
+ cpu_pda[cpu].apic_timer_irqs++;
/*
* NOTE! We'd better ACK the irq immediately,
diff -ruN -X dontdiff linux-2.5.17/arch/x86_64/kernel/irq.c apic_timer_irqs/arch/x86_64/kernel/irq.c
--- linux-2.5.17/arch/x86_64/kernel/irq.c Tue May 21 10:37:38 2002
+++ apic_timer_irqs/arch/x86_64/kernel/irq.c Fri May 24 09:58:14 2002
@@ -168,7 +168,7 @@
#if CONFIG_X86_LOCAL_APIC
seq_printf(p, "LOC: ");
for (j = 0; j < smp_num_cpus; j++)
- seq_printf(p, "%10u ", apic_timer_irqs[cpu_logical_map(j)]);
+ seq_printf(p, "%10u ", cpu_pda[cpu_logical_map(j)].apic_timer_irqs);
seq_putc(p, '\n');
#endif
seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
diff -ruN -X dontdiff linux-2.5.17/arch/x86_64/kernel/nmi.c apic_timer_irqs/arch/x86_64/kernel/nmi.c
--- linux-2.5.17/arch/x86_64/kernel/nmi.c Tue May 21 10:37:38 2002
+++ apic_timer_irqs/arch/x86_64/kernel/nmi.c Fri May 24 09:59:11 2002
@@ -240,7 +240,7 @@
*/
int sum, cpu = smp_processor_id();
- sum = apic_timer_irqs[cpu];
+ sum = cpu_pda[cpu].apic_timer_irqs;
if (last_irq_sums[cpu] == sum) {
/*
diff -ruN -X dontdiff linux-2.5.17/include/asm-i386/apic.h apic_timer_irqs/include/asm-i386/apic.h
--- linux-2.5.17/include/asm-i386/apic.h Tue May 21 10:37:38 2002
+++ apic_timer_irqs/include/asm-i386/apic.h Thu May 23 12:55:29 2002
@@ -86,7 +86,6 @@
extern struct pm_dev *apic_pm_register(pm_dev_t, unsigned long, pm_callback);
extern void apic_pm_unregister(struct pm_dev*);
-extern unsigned int apic_timer_irqs [NR_CPUS];
extern int check_nmi_watchdog (void);
extern unsigned int nmi_watchdog;
diff -ruN -X dontdiff linux-2.5.17/include/asm-i386/hardirq.h apic_timer_irqs/include/asm-i386/hardirq.h
--- linux-2.5.17/include/asm-i386/hardirq.h Tue May 21 10:37:41 2002
+++ apic_timer_irqs/include/asm-i386/hardirq.h Thu May 23 17:01:22 2002
@@ -14,6 +14,7 @@
struct task_struct * __ksoftirqd_task; /* waitqueue is too large */
unsigned long idle_timestamp;
unsigned int __nmi_count; /* arch dependent */
+ unsigned int apic_timer_irqs; /* arch dependent */
} ____cacheline_aligned irq_cpustat_t;
#include <linux/irq_cpustat.h> /* Standard mappings for irq_cpustat_t above */
diff -ruN -X dontdiff linux-2.5.17/include/asm-x86_64/apic.h apic_timer_irqs/include/asm-x86_64/apic.h
--- linux-2.5.17/include/asm-x86_64/apic.h Tue May 21 10:37:36 2002
+++ apic_timer_irqs/include/asm-x86_64/apic.h Thu May 23 17:08:07 2002
@@ -86,7 +86,6 @@
extern struct pm_dev *apic_pm_register(pm_dev_t, unsigned long, pm_callback);
extern void apic_pm_unregister(struct pm_dev*);
-extern unsigned int apic_timer_irqs [NR_CPUS];
extern int check_nmi_watchdog (void);
extern unsigned int nmi_watchdog;
diff -ruN -X dontdiff linux-2.5.17/include/asm-x86_64/pda.h apic_timer_irqs/include/asm-x86_64/pda.h
--- linux-2.5.17/include/asm-x86_64/pda.h Tue May 21 10:37:37 2002
+++ apic_timer_irqs/include/asm-x86_64/pda.h Fri May 24 09:56:03 2002
@@ -23,6 +23,7 @@
unsigned int __local_irq_count;
unsigned int __local_bh_count;
unsigned int __nmi_count; /* arch dependent */
+ unsigned int apic_timer_irqs; /* arch dependent */
struct task_struct * __ksoftirqd_task; /* waitqueue is too large */
} ____cacheline_aligned;
diff -ruN -X dontdiff linux-2.5.17/kernel/softirq.c apic_timer_irqs/kernel/softirq.c
--- linux-2.5.17/kernel/softirq.c Tue May 21 10:37:34 2002
+++ apic_timer_irqs/kernel/softirq.c Thu May 23 14:36:59 2002
@@ -40,7 +40,7 @@
- Bottom halves: globally serialized, grr...
*/
-irq_cpustat_t irq_stat[NR_CPUS];
+irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
static struct softirq_action softirq_vec[32] __cacheline_aligned_in_smp;
-
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