[patch V6 00/16] Improve /proc/interrupts further

[Thomas Gleixner <tglx@kernel.org>]

This is a follow up to v5 which can be found here:

  https://lore.kernel.org/20260401195625.213446764@kernel.org

The v1 cover letter contains a full analysis, explanation and numbers:

  https://lore.kernel.org/20260303150539.513068586@kernel.org

TLDR:

  - The performance of reading of /proc/interrupts has been improved
    piecewise over the years, but most of the low hanging fruit has been
    left on the table.

Changes vs. V5:

  - Rebased against v7.1-rc2

  - Addressed some formatting/alignment details - Radu, Michael

  - Fixed some 0-day fallout vs. various Kconfig combinations

  - Picked up tags where appropriate

Delta patch against v5 is below.

The series applies on top of v7.1-rc2 and is also available via git:

    git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git irq-proc-v6

Thanks,

	tglx
---
diff --git a/arch/alpha/kernel/irq.c b/arch/alpha/kernel/irq.c
index c67047c5d830..4a6a8b1d5a8b 100644
--- a/arch/alpha/kernel/irq.c
+++ b/arch/alpha/kernel/irq.c
@@ -72,16 +72,16 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	int j;
 
 #ifdef CONFIG_SMP
-	seq_puts(p, "IPI: ");
+	seq_puts(p, " IPI: ");
 	for_each_online_cpu(j)
 		seq_printf(p, "%10lu ", cpu_data[j].ipi_count);
 	seq_putc(p, '\n');
 #endif
-	seq_puts(p, "PMI: ");
+	seq_puts(p, " PMI: ");
 	for_each_online_cpu(j)
 		seq_printf(p, "%10lu ", per_cpu(irq_pmi_count, j));
-	seq_puts(p, "          Performance Monitoring\n");
-	seq_printf(p, "ERR: %10lu\n", irq_err_count);
+	seq_puts(p, " Performance Monitoring\n");
+	seq_printf(p, " ERR: %10lu\n", irq_err_count);
 	return 0;
 }
 
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 4e8e89a26ca3..b5fb4697bc3f 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -551,8 +551,7 @@ void show_ipi_list(struct seq_file *p, int prec)
 		if (!ipi_desc[i])
 			continue;
 
-		seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
-			   prec >= 4 ? " " : "");
+		seq_printf(p, "%*s%u:", prec - 1, "IPI", i);
 
 		for_each_online_cpu(cpu)
 			seq_printf(p, "%10u ", irq_desc_kstat_cpu(ipi_desc[i], cpu));
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 1aa324104afb..1d0e0e6a5b92 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -833,11 +833,10 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	unsigned int cpu, i;
 
 	for (i = 0; i < MAX_IPI; i++) {
-		seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
-			   prec >= 4 ? " " : "");
+		seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);
 		for_each_online_cpu(cpu)
 			seq_printf(p, "%10u ", irq_desc_kstat_cpu(get_ipi_desc(cpu, i), cpu));
-		seq_printf(p, "      %s\n", ipi_types[i]);
+		seq_printf(p, " %s\n", ipi_types[i]);
 	}
 
 	seq_printf(p, "%*s: %10lu\n", prec, "Err", irq_err_count);
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index 64a048f1b880..50922610758b 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -88,7 +88,7 @@ void show_ipi_list(struct seq_file *p, int prec)
 	unsigned int cpu, i;
 
 	for (i = 0; i < NR_IPI; i++) {
-		seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i, prec >= 4 ? " " : "");
+		seq_printf(p, "%*s%u:", prec - 1, "IPI", i);
 		for_each_online_cpu(cpu)
 			seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat, cpu).ipi_irqs[i], 10);
 		seq_printf(p, " LoongArch  %d  %s\n", i + 1, ipi_types[i]);
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 5ed5095320e6..fa66f9c97d74 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -226,8 +226,7 @@ void show_ipi_stats(struct seq_file *p, int prec)
 	unsigned int cpu, i;
 
 	for (i = 0; i < IPI_MAX; i++) {
-		seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
-			   prec >= 4 ? " " : "");
+		seq_printf(p, "%*s%u:", prec - 1, "IPI", i);
 		for_each_online_cpu(cpu)
 			seq_printf(p, "%10u ", irq_desc_kstat_cpu(ipi_desc[i], cpu));
 		seq_printf(p, " %s\n", ipi_names[i]);
diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
index 9022d8af9d68..03c39b5da50f 100644
--- a/arch/sh/kernel/irq.c
+++ b/arch/sh/kernel/irq.c
@@ -46,7 +46,7 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(j)
 		seq_put_decimal_ull_width(p, " ", per_cpu(irq_stat.__nmi_count, j), 10);
-	seq_printf(p, "  Non-maskable interrupts\n");
+	seq_printf(p, " Non-maskable interrupts\n");
 
 	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
 
diff --git a/arch/sparc/kernel/irq_32.c b/arch/sparc/kernel/irq_32.c
index 5210991429d5..22db727652ba 100644
--- a/arch/sparc/kernel/irq_32.c
+++ b/arch/sparc/kernel/irq_32.c
@@ -199,19 +199,19 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	int j;
 
 #ifdef CONFIG_SMP
-	seq_printf(p, "RES:");
+	seq_printf(p, "%*s:", prec, "RES");
 	for_each_online_cpu(j)
 		seq_put_decimal_ull_width(p, " ", cpu_data(j).irq_resched_count, 10);
-	seq_printf(p, "     IPI rescheduling interrupts\n");
-	seq_printf(p, "CAL:");
+	seq_printf(p, " IPI rescheduling interrupts\n");
+	seq_printf(p, "%*s:", prec, "CAL");
 	for_each_online_cpu(j)
 		seq_put_decimal_ull_width(p, " ", cpu_data(j).irq_call_count, 10);
-	seq_printf(p, "     IPI function call interrupts\n");
+	seq_printf(p, " IPI function call interrupts\n");
 #endif
-	seq_printf(p, "NMI:");
+	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(j)
 		seq_put_decimal_ull_width(p, " ", cpu_data(j).counter, 10);
-	seq_printf(p, "     Non-maskable interrupts\n");
+	seq_printf(p, " Non-maskable interrupts\n");
 	return 0;
 }
 
diff --git a/arch/sparc/kernel/irq_64.c b/arch/sparc/kernel/irq_64.c
index c5466a9fd560..3f55c69d5f3b 100644
--- a/arch/sparc/kernel/irq_64.c
+++ b/arch/sparc/kernel/irq_64.c
@@ -303,10 +303,10 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 {
 	int j;
 
-	seq_printf(p, "NMI:");
+	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(j)
 		seq_put_decimal_ull_width(p, " ", cpu_data(j).__nmi_count, 10);
-	seq_printf(p, "     Non-maskable interrupts\n");
+	seq_printf(p, " Non-maskable interrupts\n");
 	return 0;
 }
 
diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index 5929d498b65f..ddfd6e9bd8c7 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -716,12 +716,12 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	seq_printf(p, "%*s: ", prec, "RES");
 	for_each_online_cpu(cpu)
 		seq_printf(p, "%10u ", irq_stats(cpu)->irq_resched_count);
-	seq_puts(p, "  Rescheduling interrupts\n");
+	seq_puts(p, " Rescheduling interrupts\n");
 
 	seq_printf(p, "%*s: ", prec, "CAL");
 	for_each_online_cpu(cpu)
 		seq_printf(p, "%10u ", irq_stats(cpu)->irq_call_count);
-	seq_puts(p, "  Function call interrupts\n");
+	seq_puts(p, " Function call interrupts\n");
 #endif
 
 	return 0;
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index de1c35fa5e75..f399b993af50 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -77,54 +77,54 @@ struct irq_stat_info {
 	{ .skip_vector = DEFAULT_SUPPRESSED_VECTOR, .symbol = sym, .text = txt }
 
 static const struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] = {
-	ISS(NMI,			"NMI", "  Non-maskable interrupts\n"),
+	ISS(NMI,			"NMI",	"  Non-maskable interrupts\n"),
 #ifdef CONFIG_X86_LOCAL_APIC
-	ISS(APIC_TIMER,			"LOC", "  Local timer interrupts\n"),
-	IDS(SPURIOUS,			"SPU", "  Spurious interrupts\n"),
-	ISS(APIC_PERF,			"PMI", "  Performance monitoring interrupts\n"),
-	ISS(IRQ_WORK,			"IWI", "  IRQ work interrupts\n"),
-	IDS(ICR_READ_RETRY,		"RTR", "  APIC ICR read retries\n"),
-	ISS(X86_PLATFORM_IPI,		"PLT", "  Platform interrupts\n"),
+	ISS(APIC_TIMER,			"LOC",	"  Local timer interrupts\n"),
+	IDS(SPURIOUS,			"SPU",	"  Spurious interrupts\n"),
+	ISS(APIC_PERF,			"PMI",	"  Performance monitoring interrupts\n"),
+	ISS(IRQ_WORK,			"IWI",	"  IRQ work interrupts\n"),
+	IDS(ICR_READ_RETRY,		"RTR",	"  APIC ICR read retries\n"),
+	ISS(X86_PLATFORM_IPI,		"PLT",	"  Platform interrupts\n"),
 #endif
 #ifdef CONFIG_SMP
-	ISS(RESCHEDULE,			"RES", "  Rescheduling interrupts\n"),
-	ISS(CALL_FUNCTION,		"CAL", "  Function call interrupts\n"),
+	ISS(RESCHEDULE,			"RES",	"  Rescheduling interrupts\n"),
+	ISS(CALL_FUNCTION,		"CAL",	"  Function call interrupts\n"),
 #endif
-	ISS(TLB,			"TLB", "  TLB shootdowns\n"),
+	ISS(TLB,			"TLB",	"  TLB shootdowns\n"),
 #ifdef CONFIG_X86_THERMAL_VECTOR
-	ISS(THERMAL_APIC,		"TRM", "  Thermal event interrupt\n"),
+	ISS(THERMAL_APIC,		"TRM",	"  Thermal event interrupt\n"),
 #endif
 #ifdef CONFIG_X86_MCE_THRESHOLD
-	ISS(THRESHOLD_APIC,		"THR", "  Threshold APIC interrupts\n"),
+	ISS(THRESHOLD_APIC,		"THR",	"  Threshold APIC interrupts\n"),
 #endif
 #ifdef CONFIG_X86_MCE_AMD
-	ISS(DEFERRED_ERROR,		"DFR", "  Deferred Error APIC interrupts\n"),
+	ISS(DEFERRED_ERROR,		"DFR",	"  Deferred Error APIC interrupts\n"),
 #endif
 #ifdef CONFIG_X86_MCE
-	ISS(MCE_EXCEPTION,		"MCE", "  Machine check exceptions\n"),
-	ISS(MCE_POLL,			"MCP", "  Machine check polls\n"),
+	ISS(MCE_EXCEPTION,		"MCE",	"  Machine check exceptions\n"),
+	ISS(MCE_POLL,			"MCP",	"  Machine check polls\n"),
 #endif
 #ifdef CONFIG_X86_HV_CALLBACK_VECTOR
-	ITS(HYPERVISOR_CALLBACK,	"HYP", "  Hypervisor callback interrupts\n"),
+	ITS(HYPERVISOR_CALLBACK,	"HYP",	"  Hypervisor callback interrupts\n"),
 #endif
 #if IS_ENABLED(CONFIG_HYPERV)
-	ITS(HYPERV_REENLIGHTENMENT,	"HRE", "  Hyper-V reenlightenment interrupts\n"),
-	ITS(HYPERV_STIMER0,		"HVS", "  Hyper-V stimer0 interrupts\n"),
+	ITS(HYPERV_REENLIGHTENMENT,	"HRE",	"  Hyper-V reenlightenment interrupts\n"),
+	ITS(HYPERV_STIMER0,		"HVS",	"  Hyper-V stimer0 interrupts\n"),
 #endif
 #if IS_ENABLED(CONFIG_KVM)
-	ITS(POSTED_INTR,		"PIN", "  Posted-interrupt notification event\n"),
-	ITS(POSTED_INTR_NESTED,		"NPI", "  Nested posted-interrupt event\n"),
-	ITS(POSTED_INTR_WAKEUP,		"PIW", "  Posted-interrupt wakeup event\n"),
+	ITS(POSTED_INTR,		"PIN",	"  Posted-interrupt notification event\n"),
+	ITS(POSTED_INTR_NESTED,		"NPI",	"  Nested posted-interrupt event\n"),
+	ITS(POSTED_INTR_WAKEUP,		"PIW",	"  Posted-interrupt wakeup event\n"),
 #endif
 #ifdef CONFIG_GUEST_PERF_EVENTS
-	ISS(PERF_GUEST_MEDIATED_PMI,	"VPMI", " Perf Guest Mediated PMI\n"),
+	ISS(PERF_GUEST_MEDIATED_PMI,	"VPMI",	"  Perf Guest Mediated PMI\n"),
 #endif
 #ifdef CONFIG_X86_POSTED_MSI
-	ISS(POSTED_MSI_NOTIFICATION,	"PMN", "  Posted MSI notification event\n"),
+	ISS(POSTED_MSI_NOTIFICATION,	"PMN",	"  Posted MSI notification event\n"),
 #endif
-	IDS(PIC_APIC_ERROR,		"ERR", "  PIC/APIC error interrupts\n"),
+	IDS(PIC_APIC_ERROR,		"ERR",	"  PIC/APIC error interrupts\n"),
 #ifdef CONFIG_X86_IO_APIC
-	IDS(IOAPIC_MISROUTED,		"MIS", "  Misrouted IO/APIC interrupts\n"),
+	IDS(IOAPIC_MISROUTED,		"MIS",	"  Misrouted IO/APIC interrupts\n"),
 #endif
 };
 
diff --git a/arch/xtensa/kernel/irq.c b/arch/xtensa/kernel/irq.c
index b1e410f6b5ab..6f01f530868b 100644
--- a/arch/xtensa/kernel/irq.c
+++ b/arch/xtensa/kernel/irq.c
@@ -59,7 +59,7 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	seq_printf(p, "%*s:", prec, "NMI");
 	for_each_online_cpu(cpu)
 		seq_printf(p, " %10lu", per_cpu(nmi_count, cpu));
-	seq_puts(p, "   Non-maskable interrupts\n");
+	seq_puts(p, " Non-maskable interrupts\n");
 #endif
 	return 0;
 }
diff --git a/kernel/irq/debugfs.h b/kernel/irq/debugfs.h
new file mode 100644
index 000000000000..8a9360d5fefb
--- /dev/null
+++ b/kernel/irq/debugfs.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KERNEL_IRQ_DEBUGFS_H
+#define _KERNEL_IRQ_DEBUGFS_H
+
+#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+#include <linux/debugfs.h>
+
+struct irq_bit_descr {
+	unsigned int	mask;
+	char		*name;
+};
+
+#define BIT_MASK_DESCR(m)	{ .mask = m, .name = #m }
+
+void irq_debug_show_bits(struct seq_file *m, int ind, unsigned int state,
+			 const struct irq_bit_descr *sd, int size);
+
+void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc);
+static inline void irq_remove_debugfs_entry(struct irq_desc *desc)
+{
+	debugfs_remove(desc->debugfs_file);
+	kfree(desc->dev_name);
+}
+void irq_debugfs_copy_devname(int irq, struct device *dev);
+# ifdef CONFIG_IRQ_DOMAIN
+void irq_domain_debugfs_init(struct dentry *root);
+# else
+static inline void irq_domain_debugfs_init(struct dentry *root)
+{
+}
+# endif
+#else /* CONFIG_GENERIC_IRQ_DEBUGFS */
+static inline void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *d)
+{
+}
+static inline void irq_remove_debugfs_entry(struct irq_desc *d)
+{
+}
+static inline void irq_debugfs_copy_devname(int irq, struct device *dev)
+{
+}
+#endif /* CONFIG_GENERIC_IRQ_DEBUGFS */
+
+#endif
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 7fbf003c6e93..f9c099d45a64 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -12,6 +12,7 @@
 #include <linux/rcuref.h>
 #include <linux/sched/clock.h>
 
+#include "debugfs.h"
 #include "proc.h"
 
 #ifdef CONFIG_SPARSE_IRQ
@@ -394,42 +395,3 @@ static inline struct irq_data *irqd_get_parent_data(struct irq_data *irqd)
 	return NULL;
 #endif
 }
-
-#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
-#include <linux/debugfs.h>
-
-struct irq_bit_descr {
-	unsigned int	mask;
-	char		*name;
-};
-
-#define BIT_MASK_DESCR(m)	{ .mask = m, .name = #m }
-
-void irq_debug_show_bits(struct seq_file *m, int ind, unsigned int state,
-			 const struct irq_bit_descr *sd, int size);
-
-void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc);
-static inline void irq_remove_debugfs_entry(struct irq_desc *desc)
-{
-	debugfs_remove(desc->debugfs_file);
-	kfree(desc->dev_name);
-}
-void irq_debugfs_copy_devname(int irq, struct device *dev);
-# ifdef CONFIG_IRQ_DOMAIN
-void irq_domain_debugfs_init(struct dentry *root);
-# else
-static inline void irq_domain_debugfs_init(struct dentry *root)
-{
-}
-# endif
-#else /* CONFIG_GENERIC_IRQ_DEBUGFS */
-static inline void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *d)
-{
-}
-static inline void irq_remove_debugfs_entry(struct irq_desc *d)
-{
-}
-static inline void irq_debugfs_copy_devname(int irq, struct device *dev)
-{
-}
-#endif /* CONFIG_GENERIC_IRQ_DEBUGFS */
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 9f524ed709b8..f15c9f1223bb 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -2084,7 +2084,7 @@ static void irq_domain_free_one_irq(struct irq_domain *domain, unsigned int virq
 #endif	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
 
 #ifdef CONFIG_GENERIC_IRQ_DEBUGFS
-#include "internals.h"
+#include "debugfs.h"
 
 static struct dentry *domain_dir;
 
diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
index 3bd394aa7617..ca535472e657 100644
--- a/kernel/irq/proc.c
+++ b/kernel/irq/proc.c
@@ -465,7 +465,7 @@ static struct irq_proc_constraints {
 	unsigned int	num_prec;
 	unsigned int	chip_width;
 } irq_proc_constraints __read_mostly = {
-	.num_prec	= 3,
+	.num_prec	= 4,
 	.chip_width	= 8,
 };
 
@@ -477,7 +477,7 @@ void irq_proc_calc_prec(void)
 {
 	unsigned int prec, n;
 
-	for (prec = 3, n = 1000; prec < 10 && n <= total_nr_irqs; ++prec)
+	for (prec = 4, n = 10000; prec < 10 && n <= total_nr_irqs; ++prec)
 		n *= 10;
 
 	guard(raw_spinlock_irqsave)(&irq_proc_constraints_lock);
@@ -498,6 +498,7 @@ void irq_proc_update_chip(const struct irq_chip *chip)
 		WRITE_ONCE(irq_proc_constraints.chip_width, len);
 }
 
+/* Same as seq_put_decimal_ull_width(p, " ", cnt, 10) */
 #define ZSTR1 "          0"
 #define ZSTR1_LEN	(sizeof(ZSTR1) - 1)
 #define ZSTR16		ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 \
diff --git a/kernel/irq/proc.h b/kernel/irq/proc.h
index ec9173d573f9..0631d57fbfb7 100644
--- a/kernel/irq/proc.h
+++ b/kernel/irq/proc.h
@@ -1,4 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _KERNEL_IRQ_PROC_H
+#define _KERNEL_IRQ_PROC_H
 
 #if defined(CONFIG_PROC_FS) && defined(CONFIG_GENERIC_IRQ_SHOW)
 void irq_proc_calc_prec(void);
@@ -7,3 +9,5 @@ void irq_proc_update_chip(const struct irq_chip *chip);
 static inline void irq_proc_calc_prec(void) { }
 static inline void irq_proc_update_chip(const struct irq_chip *chip) { }
 #endif
+
+#endif
diff --git a/scripts/gdb/linux/interrupts.py b/scripts/gdb/linux/interrupts.py
index cf0a02c8124d..a68ae91b4531 100644
--- a/scripts/gdb/linux/interrupts.py
+++ b/scripts/gdb/linux/interrupts.py
@@ -90,6 +90,13 @@ def show_irq_desc(prec, chip_width, irq):
 
     return text
 
+def show_irq_err_count(prec):
+    cnt = utils.gdb_eval_or_none("irq_err_count")
+    text = ""
+    if cnt is not None:
+        text += "%*s: %10u\n" % (prec, "ERR", cnt['counter'])
+    return text
+
 def x86_show_irqstat(prec, pfx, idx, desc):
     irq_stat = gdb.parse_and_eval("&irq_stat.counts[%d]" %idx)
     text = "%*s: " % (prec, pfx)
@@ -124,34 +131,23 @@ def arm_common_show_interrupts(prec):
     if nr_ipi is None or ipi_desc is None or ipi_types is None:
         return text
 
-    if prec >= 4:
-        sep = " "
-    else:
-        sep = ""
-
     for ipi in range(nr_ipi):
-        text += "%*s%u:%s" % (prec - 1, "IPI", ipi, sep)
+        text += "%*s%u: " % (prec - 1, "IPI", ipi)
         desc = ipi_desc[ipi].cast(irq_desc_type.get_type().pointer())
         if desc == 0:
             continue
         for cpu in cpus.each_online_cpu():
-            text += "%10u" % (cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt'])
-        text += "      %s" % (ipi_types[ipi].string())
+            text += "%10u " % (cpus.per_cpu(desc['kstat_irqs'], cpu)['cnt'])
+        text += "%s" % (ipi_types[ipi].string())
         text += "\n"
     return text
 
 def aarch64_show_interrupts(prec):
+    # Does not work for ARM64 as "ipi_desc" is not available there
     text = arm_common_show_interrupts(prec)
     text += "%*s: %10lu\n" % (prec, "ERR", gdb.parse_and_eval("irq_err_count"))
     return text
 
-def show_irq_err_count(prec):
-    cnt = utils.gdb_eval_or_none("irq_err_count")
-    text = ""
-    if cnt is not None:
-        text += "%*s: %10u\n" % (prec, "ERR", cnt['counter'])
-    return text
-
 def arch_show_interrupts(prec):
     text = ""
     if utils.is_target_arch("x86"):
@@ -181,8 +177,8 @@ class LxInterruptList(gdb.Command):
             prec = int(constr['num_prec'])
             chip_width = int(constr['chip_width'])
         else:
-            prec = 3
-            j = 1000
+            prec = 4
+            j = 10000
             while prec < 10 and j <= nr_irqs:
                 prec += 1
                 j *= 10