[PATCH v2 0/3] powerpc/irq: Use optimizations for /proc/interrupts

[PATCH v2 0/3] powerpc/irq: Use optimizations for /proc/interrupts

[Shrikanth Hegde]

v1-> v2:
- Collected the tags (Thanks to Christophe Leroy)
- Rename skip to optional and check optional while printing
  (Christophe Leroy)
- Decided not to add cpu_has_feature(CPU_FTR_DBELL) while printing.
  This feature is mostly true for majority of platforms and adding check
  means more ifdefs in that path. Prinitng "Doorbell interrupts" shouldn't
  cause any issue when feature if off since all entries would be zero.
  (sashiko)

This series is based on work by Thomas Gleixner[1].
Further details can be found in cover-letter of v1.

======== Performance Data ==================
Time taken to read /proc/interrupts 1000 times[2]
Base		:  103us 
v6[1]		:   63us
v6+patch 1+2	:   57us
v6+patch 1+2+3	:   54us

Base: tip/master at 'ddfd3966d0d4 ("Merge branch into tip/master: 'x86/tdx'")'

[1]: https://lore.kernel.org/all/20260517194421.705253664@kernel.org/
[2]: https://lore.kernel.org/all/87jysxw65f.ffs@tglx/
v1: https://lore.kernel.org/all/20260523174016.999456-1-sshegde@linux.ibm.com/

Shrikanth Hegde (3):
  powerpc/irq: Move __softirq_pending out of irq_stat
  powerpc/irq: Make irqstats array based
  powerpc/irq: Suppress unlikely interrupt stats by default

 arch/powerpc/include/asm/hardirq.h |  31 ++++---
 arch/powerpc/kernel/dbell.c        |   2 +-
 arch/powerpc/kernel/irq.c          | 131 +++++++++++++++--------------
 arch/powerpc/kernel/time.c         |   6 +-
 arch/powerpc/kernel/traps.c        |  11 +--
 arch/powerpc/kernel/watchdog.c     |   2 +-
 6 files changed, 95 insertions(+), 88 deletions(-)

-- 
2.47.3

[PATCH v2 1/3] powerpc/irq: Move __softirq_pending out of irq_stat

[Shrikanth Hegde]

__softirq_pending isn't part of arch specific irq_stats. It is used
by softirq core for various decision making such as whether to kick off
ksoftirqd.

Move it out of irq_cpustat_t. This makes it simple to make irq_cpustat_t
array based approach.

Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 arch/powerpc/include/asm/hardirq.h | 3 ++-
 arch/powerpc/kernel/irq.c          | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/hardirq.h b/arch/powerpc/include/asm/hardirq.h
index f133b5930ae1..bf3926a0c69c 100644
--- a/arch/powerpc/include/asm/hardirq.h
+++ b/arch/powerpc/include/asm/hardirq.h
@@ -6,7 +6,6 @@
 #include <linux/irq.h>
 
 typedef struct {
-	unsigned int __softirq_pending;
 	unsigned int timer_irqs_event;
 	unsigned int broadcast_irqs_event;
 	unsigned int timer_irqs_others;
@@ -23,6 +22,8 @@ typedef struct {
 } ____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 __ARCH_IRQ_STAT
 #define __ARCH_IRQ_EXIT_IRQS_DISABLED
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index a0e8b998c9b5..f33df5e5c23f 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -73,6 +73,7 @@
 
 DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
 EXPORT_PER_CPU_SYMBOL(irq_stat);
+DEFINE_PER_CPU(unsigned int, __softirq_pending);
 
 #ifdef CONFIG_PPC32
 atomic_t ppc_n_lost_interrupts;
-- 
2.47.3

[PATCH v2 2/3] powerpc/irq: Make irqstats array based

[Shrikanth Hegde]

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>
---
 arch/powerpc/include/asm/hardirq.h |  27 +++++---
 arch/powerpc/kernel/dbell.c        |   2 +-
 arch/powerpc/kernel/irq.c          | 107 ++++++++++-------------------
 arch/powerpc/kernel/time.c         |   6 +-
 arch/powerpc/kernel/traps.c        |  11 ++-
 arch/powerpc/kernel/watchdog.c     |   2 +-
 6 files changed, 64 insertions(+), 91 deletions(-)

diff --git a/arch/powerpc/include/asm/hardirq.h b/arch/powerpc/include/asm/hardirq.h
index bf3926a0c69c..38098e35b241 100644
--- a/arch/powerpc/include/asm/hardirq.h
+++ b/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
 
diff --git a/arch/powerpc/kernel/dbell.c b/arch/powerpc/kernel/dbell.c
index 5712dd846263..f5e298a4c4c0 100644
--- a/arch/powerpc/kernel/dbell.c
+++ b/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 */
 
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index f33df5e5c23f..e67a18f62142 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/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;
 }
 
@@ -248,7 +217,7 @@ 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);
 
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index b4472288e0d4..5794adc2e8df 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -574,13 +574,13 @@ 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);
@@ -593,7 +593,7 @@ 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
 
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index cb8e9357383e..a8f15154bd9a 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/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);
 }
 
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c
index 764001deb060..f516eeccc9f6 100644
--- a/arch/powerpc/kernel/watchdog.c
+++ b/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) {
-- 
2.47.3

[PATCH v2 3/3] powerpc/irq: Suppress unlikely interrupt stats by default

[Shrikanth Hegde]

Some interrupts are always zero and that is expected since they occur
very rarely and are mostly error indications. Don't print them by
default.

"MCE" -  "Machine check exceptions"
"NMI" -  "System Reset interrupts"

Print them if they occur once. Maintain a bitmap to know which
interrupts are to be printed.

Time taken to read /proc/interrupts 1000 times.
Base and v6 details can be found in cover-letter.
Base            :  103us
v6              :   63us
v6+patch 1+2    :   57us
v6+patch 1+2+3  :   54us

Patch 3 shows an additional 5% gain compared to patch 1+2. So it does
make sense to print them only if they are ever set.

Note: Since /proc/interrupts depend on kconfig and arch dependent,
userspace tools don't make explicit assumptions.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 arch/powerpc/include/asm/hardirq.h |  1 +
 arch/powerpc/kernel/irq.c          | 37 +++++++++++++++++++++++++++---
 arch/powerpc/kernel/traps.c        |  4 ++--
 3 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/hardirq.h b/arch/powerpc/include/asm/hardirq.h
index 38098e35b241..be6cd5aab016 100644
--- a/arch/powerpc/include/asm/hardirq.h
+++ b/arch/powerpc/include/asm/hardirq.h
@@ -31,6 +31,7 @@ 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])
+void inc_irq_stat_and_enable(enum irq_stat_counts which);
 
 #define __ARCH_IRQ_STAT
 #define __ARCH_IRQ_EXIT_IRQS_DISABLED
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index e67a18f62142..0a6a0e707fe8 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -87,9 +87,13 @@ u32 tau_interrupts(unsigned long cpu);
 struct irq_stat_info {
 	const char	*symbol;
 	const char	*text;
+	int		optional;
 };
 
-#define ISE(idx, sym, txt)[IRQ_COUNT_##idx] = { .symbol = sym, .text = txt}
+/* ISE - IRQ STAT ENABLED, ISC - IRQ STAT CONDITIONAL */
+#define ISE(idx, sym, txt)[IRQ_COUNT_##idx] = { .symbol = sym, .text = txt, .optional = 0}
+#define ISC(idx, sym, txt)[IRQ_COUNT_##idx] = { .symbol = sym, .text = txt, .optional = 1}
+
 
 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"),
@@ -97,8 +101,8 @@ static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
 	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"),
+	ISC(MCE,		"MCE", "  Machine check exceptions\n"),
+	ISC(NMI_SRESET,		"NMI", "  System Reset interrupts\n"),
 #ifdef CONFIG_PPC_WATCHDOG
 	ISE(WATCHDOG,		"WDG", "  Watchdog soft-NMI interrupts\n"),
 #endif
@@ -107,11 +111,25 @@ static struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] __ro_after_init = {
 #endif
 };
 
+/*
+ * Used for default disabled counters to increment the stats and to enable the
+ * entry for /proc/interrupts output.
+ */
+static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;
+void inc_irq_stat_and_enable(enum irq_stat_counts which)
+{
+	__this_cpu_inc(irq_stat.counts[which]);
+	set_bit(which, irq_stat_count_show);
+}
+
 int arch_show_interrupts(struct seq_file *p, int prec)
 {
 	const struct irq_stat_info *info = irq_stat_info;
 
 	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
+		if (info->optional && !test_bit(i, irq_stat_count_show))
+			continue;
+
 		seq_printf(p, "%*s:", prec, info->symbol);
 		irq_proc_emit_counts(p, &irq_stat.counts[i]);
 		seq_puts(p, info->text);
@@ -138,6 +156,19 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	return 0;
 }
 
+static int __init irq_init_stats(void)
+{
+	struct irq_stat_info *info = irq_stat_info;
+
+	for (unsigned int i = 0; i < ARRAY_SIZE(irq_stat_info); i++, info++) {
+		if (info->optional == 0)
+			set_bit(i, irq_stat_count_show);
+	}
+
+	return 0;
+}
+late_initcall(irq_init_stats);
+
 /*
  * /proc/stat helpers
  */
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index a8f15154bd9a..3eacbd20fc80 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -459,7 +459,7 @@ DEFINE_INTERRUPT_HANDLER_NMI(system_reset_exception)
 	}
 
 	hv_nmi_check_nonrecoverable(regs);
-	inc_irq_stat(NMI_SRESET);
+	inc_irq_stat_and_enable(IRQ_COUNT_NMI_SRESET);
 
 	/* See if any machine dependent calls */
 	if (ppc_md.system_reset_exception) {
@@ -816,7 +816,7 @@ static void __machine_check_exception(struct pt_regs *regs)
 {
 	int recover = 0;
 
-	inc_irq_stat(MCE);
+	inc_irq_stat_and_enable(IRQ_COUNT_MCE);
 
 	add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE);
 
-- 
2.47.3