powerpc/irq: Make irqstats array based

Current irq_cpustat_t has separate member for handling each arch
specific interrupt type. The same can be achieved with array instead
indexed by corresponding irq counter type.

This helps to,

- Make it easy to integrate into genirq improvements by calling
  genirq provided irq_proc_emit_counts. That speeds up quite a bit
  by printing all 0's once as much as possible.

- Adding a new vector or software counter only requires to update the table
  and everything just works

- Remove ifdef usage a bit.

- Instead of going through each member, it simply becomes an array
  traversal.

Time taken to read /proc/interrupts 1000 times.
Base and v6 details can be found in cover-letter.
Base		:  103us
v6		:   63us
v6+this_patch	:   57us

A Decent 10% reduction can be seen in a system 240 CPUs. As the system
size increases the gain would be more as emitting 0 would reduce more
and more.

Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260921090153.54745-3-sshegde@linux.ibm.com

arch/powerpc/include/asm/hardirq.h

@@ -5,26 +5,33 @@
 #include <linux/threads.h>
 #include <linux/irq.h>
 
-typedef struct {
-	unsigned int timer_irqs_event;
-	unsigned int broadcast_irqs_event;
-	unsigned int timer_irqs_others;
-	unsigned int pmu_irqs;
-	unsigned int mce_exceptions;
-	unsigned int spurious_irqs;
-	unsigned int sreset_irqs;
+enum irq_stat_counts {
+	IRQ_COUNT_LOC_TIMER,
+	IRQ_COUNT_BCT_TIMER,
+	IRQ_COUNT_OTHER_TIMER,
+	IRQ_COUNT_SPURIOUS,
+	IRQ_COUNT_PMI,
+	IRQ_COUNT_MCE,
+	IRQ_COUNT_NMI_SRESET,
 #ifdef CONFIG_PPC_WATCHDOG
-	unsigned int soft_nmi_irqs;
+	IRQ_COUNT_WATCHDOG,
 #endif
 #ifdef CONFIG_PPC_DOORBELL
-	unsigned int doorbell_irqs;
+	IRQ_COUNT_DOORBELL,
 #endif
+	IRQ_COUNT_MAX,
+};
+
+typedef struct {
+	unsigned int counts[IRQ_COUNT_MAX];
 } ____cacheline_aligned irq_cpustat_t;
 
 DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 DECLARE_PER_CPU(unsigned int, __softirq_pending);
 #define local_softirq_pending_ref       __softirq_pending
 
+#define inc_irq_stat(index)	__this_cpu_inc(irq_stat.counts[IRQ_COUNT_##index])
+
 #define __ARCH_IRQ_STAT
 #define __ARCH_IRQ_EXIT_IRQS_DISABLED
 

arch/powerpc/kernel/dbell.c

@@ -31,7 +31,7 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(doorbell_exception)
 		do_hard_irq_enable();
 
 	kvmppc_clear_host_ipi(smp_processor_id());
-	__this_cpu_inc(irq_stat.doorbell_irqs);
+	inc_irq_stat(DOORBELL);
 
 	smp_ipi_demux_relaxed(); /* already performed the barrier */
 

arch/powerpc/kernel/irq.c

@@ -84,79 +84,57 @@ u32 tau_interrupts(unsigned long cpu);
 #endif
 #endif /* CONFIG_PPC32 */
 
+struct irq_stat_info {
+	const char	*symbol;
+	const char	*text;
+};
+
+#define ISE(idx, sym, txt)[IRQ_COUNT_##idx] = { .symbol = sym, .text = txt}
+
+static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
+	ISE(LOC_TIMER,		"LOC", "  Local timer interrupts for timer event device\n"),
+	ISE(BCT_TIMER,		"BCT", "  Broadcast timer interrupts for timer event device\n"),
+	ISE(OTHER_TIMER,	"LOC", "  Local timer interrupts for others\n"),
+	ISE(SPURIOUS,		"SPU", "  Spurious interrupts\n"),
+	ISE(PMI,		"PMI", "  Performance monitoring interrupts\n"),
+	ISE(MCE,		"MCE", "  Machine check exceptions\n"),
+	ISE(NMI_SRESET,		"NMI", "  System Reset interrupts\n"),
+#ifdef CONFIG_PPC_WATCHDOG
+	ISE(WATCHDOG,		"WDG", "  Watchdog soft-NMI interrupts\n"),
+#endif
+#ifdef CONFIG_PPC_DOORBELL
+	ISE(DOORBELL,		"DBL", "  Doorbell interrupts\n"),
+#endif
+};
+
 int arch_show_interrupts(struct seq_file *p, int prec)
 {
-	int j;
+	const struct irq_stat_info *info = irq_stat_info;
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
+		seq_printf(p, "%*s:", prec, info->symbol);
+		irq_proc_emit_counts(p, &irq_stat.counts[i]);
+		seq_puts(p, info->text);
+	}
 
 #if defined(CONFIG_PPC32) && defined(CONFIG_TAU_INT)
 	if (tau_initialized) {
+		int j;
 		seq_printf(p, "%*s:", prec, "TAU");
 		for_each_online_cpu(j)
 			seq_put_decimal_ull_width(p, " ", tau_interrupts(j), 10);
 		seq_puts(p, "  PowerPC             Thermal Assist (cpu temp)\n");
 	}
 #endif /* CONFIG_PPC32 && CONFIG_TAU_INT */
-
-	seq_printf(p, "%*s:", prec, "LOC");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).timer_irqs_event, 10);
-        seq_printf(p, "  Local timer interrupts for timer event device\n");
-
-	seq_printf(p, "%*s:", prec, "BCT");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).broadcast_irqs_event, 10);
-	seq_printf(p, "  Broadcast timer interrupts for timer event device\n");
-
-	seq_printf(p, "%*s:", prec, "LOC");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).timer_irqs_others, 10);
-        seq_printf(p, "  Local timer interrupts for others\n");
-
-	seq_printf(p, "%*s:", prec, "SPU");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).spurious_irqs, 10);
-	seq_printf(p, "  Spurious interrupts\n");
-
-	seq_printf(p, "%*s:", prec, "PMI");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).pmu_irqs, 10);
-	seq_printf(p, "  Performance monitoring interrupts\n");
-
-	seq_printf(p, "%*s:", prec, "MCE");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).mce_exceptions, 10);
-	seq_printf(p, "  Machine check exceptions\n");
-
 #ifdef CONFIG_PPC_BOOK3S_64
 	if (cpu_has_feature(CPU_FTR_HVMODE)) {
+		int j;
 		seq_printf(p, "%*s:", prec, "HMI");
 		for_each_online_cpu(j)
 			seq_put_decimal_ull_width(p, " ", paca_ptrs[j]->hmi_irqs, 10);
 		seq_printf(p, "  Hypervisor Maintenance Interrupts\n");
 	}
 #endif
-
-	seq_printf(p, "%*s:", prec, "NMI");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).sreset_irqs, 10);
-	seq_printf(p, "  System Reset interrupts\n");
-
-#ifdef CONFIG_PPC_WATCHDOG
-	seq_printf(p, "%*s:", prec, "WDG");
-	for_each_online_cpu(j)
-		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).soft_nmi_irqs, 10);
-	seq_printf(p, "  Watchdog soft-NMI interrupts\n");
-#endif
-
-#ifdef CONFIG_PPC_DOORBELL
-	if (cpu_has_feature(CPU_FTR_DBELL)) {
-		seq_printf(p, "%*s:", prec, "DBL");
-		for_each_online_cpu(j)
-			seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, j).doorbell_irqs, 10);
-		seq_printf(p, "  Doorbell interrupts\n");
-	}
-#endif
-
 	return 0;
 }
 
@@ -165,24 +143,15 @@ int arch_show_interrupts(struct seq_file *p, int prec)
  */
 u64 arch_irq_stat_cpu(unsigned int cpu)
 {
-	u64 sum = per_cpu(irq_stat, cpu).timer_irqs_event;
+	irq_cpustat_t *p = per_cpu_ptr(&irq_stat, cpu);
+	u64 sum = 0;
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++)
+		sum += p->counts[i];
 
-	sum += per_cpu(irq_stat, cpu).broadcast_irqs_event;
-	sum += per_cpu(irq_stat, cpu).pmu_irqs;
-	sum += per_cpu(irq_stat, cpu).mce_exceptions;
-	sum += per_cpu(irq_stat, cpu).spurious_irqs;
-	sum += per_cpu(irq_stat, cpu).timer_irqs_others;
 #ifdef CONFIG_PPC_BOOK3S_64
 	sum += paca_ptrs[cpu]->hmi_irqs;
 #endif
-	sum += per_cpu(irq_stat, cpu).sreset_irqs;
-#ifdef CONFIG_PPC_WATCHDOG
-	sum += per_cpu(irq_stat, cpu).soft_nmi_irqs;
-#endif
-#ifdef CONFIG_PPC_DOORBELL
-	sum += per_cpu(irq_stat, cpu).doorbell_irqs;
-#endif
-
 	return sum;
 }
 
@@ -252,7 +221,7 @@ static void __do_irq(struct pt_regs *regs, unsigned long oldsp)
 
 	/* And finally process it */
 	if (unlikely(!irq))
-		__this_cpu_inc(irq_stat.spurious_irqs);
+		inc_irq_stat(SPURIOUS);
 	else
 		generic_handle_irq(irq);
 

arch/powerpc/kernel/time.c

@@ -615,13 +615,13 @@ DEFINE_INTERRUPT_HANDLER_ASYNC(timer_interrupt)
 	now = get_tb();
 	if (now >= *next_tb) {
 		evt->event_handler(evt);
-		__this_cpu_inc(irq_stat.timer_irqs_event);
+		inc_irq_stat(LOC_TIMER);
 	} else {
 		now = *next_tb - now;
 		if (now > decrementer_max)
 			now = decrementer_max;
 		set_dec_or_work(now);
-		__this_cpu_inc(irq_stat.timer_irqs_others);
+		inc_irq_stat(OTHER_TIMER);
 	}
 
 	trace_timer_interrupt_exit(regs);
@@ -634,7 +634,7 @@ EXPORT_SYMBOL(timer_interrupt);
 void timer_broadcast_interrupt(void)
 {
 	tick_receive_broadcast();
-	__this_cpu_inc(irq_stat.broadcast_irqs_event);
+	inc_irq_stat(BCT_TIMER);
 }
 #endif
 

arch/powerpc/kernel/traps.c

@@ -459,8 +459,7 @@ DEFINE_INTERRUPT_HANDLER_NMI(system_reset_exception)
 	}
 
 	hv_nmi_check_nonrecoverable(regs);
-
-	__this_cpu_inc(irq_stat.sreset_irqs);
+	inc_irq_stat(NMI_SRESET);
 
 	/* See if any machine dependent calls */
 	if (ppc_md.system_reset_exception) {
@@ -817,7 +816,7 @@ static void __machine_check_exception(struct pt_regs *regs)
 {
 	int recover = 0;
 
-	__this_cpu_inc(irq_stat.mce_exceptions);
+	inc_irq_stat(MCE);
 
 	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
 
@@ -1932,8 +1931,7 @@ DEFINE_INTERRUPT_HANDLER(vsx_unavailable_tm)
 DECLARE_INTERRUPT_HANDLER_NMI(performance_monitor_exception_nmi);
 DEFINE_INTERRUPT_HANDLER_NMI(performance_monitor_exception_nmi)
 {
-	__this_cpu_inc(irq_stat.pmu_irqs);
-
+	inc_irq_stat(PMI);
 	perf_irq(regs);
 
 	return 0;
@@ -1943,8 +1941,7 @@ DEFINE_INTERRUPT_HANDLER_NMI(performance_monitor_exception_nmi)
 DECLARE_INTERRUPT_HANDLER_ASYNC(performance_monitor_exception_async);
 DEFINE_INTERRUPT_HANDLER_ASYNC(performance_monitor_exception_async)
 {
-	__this_cpu_inc(irq_stat.pmu_irqs);
-
+	inc_irq_stat(PMI);
 	perf_irq(regs);
 }
 

arch/powerpc/kernel/watchdog.c

@@ -381,7 +381,7 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt)
 	if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
 		return 0;
 
-	__this_cpu_inc(irq_stat.soft_nmi_irqs);
+	inc_irq_stat(WATCHDOG);
 
 	tb = get_tb();
 	if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {