RE: [patch 04/14] x86/irq: Make irqstats array based

[Michael Kelley]

From: Thomas Gleixner <tglx@xxxxxxxxxx> Sent: Wednesday, March 4, 2026 10:56 AM
> 
> Having the x86 specific interrupt statistics as a data structure with
> individual members instead of an array is just stupid as it requires
> endless copy and paste in arch_show_interrupts() and arch_irq_stat_cpu(),
> where the latter does not even take the latest interrupt additions into
> account. The resulting #ifdef orgy is just disgusting.
> 
> Convert it to an array of counters, which does not make a difference in the
> actual interrupt hotpath increment as the array index is constant and
> therefore not any different than the member based access.
> 
> But in arch_show_interrupts() and arch_irq_stat_cpu() this just turns into
> a loop, which reduces the text size by ~2k (~12%):
> 
>    text	   data	    bss	    dec	    hex	filename
>   19643	  15250	    904	  35797	   8bd5	../build/arch/x86/kernel/irq.o
>   17355	  15250	    904	  33509	   82e5	../build/arch/x86/kernel/irq.o
> 
> Adding a new vector or software counter only requires to update the table
> and everything just works. Using the core provided emit function which
> speeds up 0 outputs makes it significantly faster.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
> ---
>  arch/x86/events/amd/core.c          |    2
>  arch/x86/events/amd/ibs.c           |    2
>  arch/x86/events/core.c              |    2
>  arch/x86/events/intel/core.c        |    2
>  arch/x86/events/intel/knc.c         |    2
>  arch/x86/events/intel/p4.c          |    2
>  arch/x86/events/zhaoxin/core.c      |    2
>  arch/x86/hyperv/hv_init.c           |    2
>  arch/x86/include/asm/hardirq.h      |   69 ++++++----
>  arch/x86/include/asm/mce.h          |    3
>  arch/x86/kernel/apic/apic.c         |    4
>  arch/x86/kernel/apic/ipi.c          |    2
>  arch/x86/kernel/cpu/acrn.c          |    2
>  arch/x86/kernel/cpu/mce/amd.c       |    2
>  arch/x86/kernel/cpu/mce/core.c      |    8 -
>  arch/x86/kernel/cpu/mce/threshold.c |    2
>  arch/x86/kernel/cpu/mshyperv.c      |    4
>  arch/x86/kernel/irq.c               |  227 ++++++++++--------------------------
>  arch/x86/kernel/irq_work.c          |    2
>  arch/x86/kernel/kvm.c               |    2
>  arch/x86/kernel/nmi.c               |    4
>  arch/x86/kernel/smp.c               |    6
>  arch/x86/mm/tlb.c                   |    2
>  arch/x86/xen/enlighten_hvm.c        |    2
>  arch/x86/xen/enlighten_pv.c         |    2
>  arch/x86/xen/smp.c                  |    6
>  arch/x86/xen/smp_pv.c               |    2
>  27 files changed, 135 insertions(+), 232 deletions(-)
> 

[snip]

> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -154,7 +154,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_cal
>  {
>  	struct pt_regs *old_regs = set_irq_regs(regs);
> 
> -	inc_irq_stat(irq_hv_callback_count);
> +	inc_irq_stat(HYPERVISOR_CALLBACK);
>  	if (mshv_handler)
>  		mshv_handler();
> 
> @@ -191,7 +191,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_sti
>  {
>  	struct pt_regs *old_regs = set_irq_regs(regs);
> 
> -	inc_irq_stat(hyperv_stimer0_count);
> +	inc_irq_stat(HYPERV_STIMER0)

Missing semicolon at the end of this line causes a compile error.

>  	if (hv_stimer0_handler)
>  		hv_stimer0_handler();
>  	add_interrupt_randomness(HYPERV_STIMER0_VECTOR);
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -62,156 +62,84 @@ void ack_bad_irq(unsigned int irq)
>  	apic_eoi();
>  }
> 
> -/*
> - * A helper routine for putting space and decimal number without overhead
> - * from rich format of printf().
> - */
> -static void put_decimal(struct seq_file *p, unsigned long long num)
> -{
> -	const char *delimiter = " ";
> -	unsigned int width = 10;
> +struct irq_stat_info {
> +	unsigned int	test_vector;
> +	const char	*symbol;
> +	const char	*text;
> +};
> 
> -	seq_put_decimal_ull_width(p, delimiter, num, width);
> -}
> +#define ISS(idx, sym, txt) [IRQ_COUNT_##idx] = { .symbol = sym, .text = txt }
> 
> -#define irq_stats(x)		(&per_cpu(irq_stat, x))
> -/*
> - * /proc/interrupts printing for arch specific interrupts
> - */
> -int arch_show_interrupts(struct seq_file *p, int prec)
> -{
> -	int j;
> +#define ITS(idx, sym, txt) [IRQ_COUNT_##idx] =				\
> +	{ .test_vector = idx## _VECTOR, .symbol = sym, .text = txt }
> 
> -	seq_printf(p, "%*s:", prec, "NMI");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->__nmi_count);
> -	seq_puts(p, "  Non-maskable interrupts\n");
> +static const struct irq_stat_info irq_stat_info[IRQ_COUNT_MAX] = {
> +	ISS(NMI,			"NMI", " Non-maskable interrupts\n"),
>  #ifdef CONFIG_X86_LOCAL_APIC
> -	seq_printf(p, "%*s:", prec, "LOC");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->apic_timer_irqs);
> -	seq_puts(p, "  Local timer interrupts\n");
> -
> -	seq_printf(p, "%*s:", prec, "SPU");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_spurious_count);
> -	seq_puts(p, "  Spurious interrupts\n");
> -	seq_printf(p, "%*s:", prec, "PMI");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->apic_perf_irqs);
> -	seq_puts(p, "  Performance monitoring interrupts\n");
> -	seq_printf(p, "%*s:", prec, "IWI");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->apic_irq_work_irqs);
> -	seq_puts(p, "  IRQ work interrupts\n");
> -	seq_printf(p, "%*s:", prec, "RTR");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->icr_read_retry_count);
> -	seq_puts(p, "  APIC ICR read retries\n");
> -	if (x86_platform_ipi_callback) {
> -		seq_printf(p, "%*s:", prec, "PLT");
> -		for_each_online_cpu(j)
> -			put_decimal(p, irq_stats(j)->x86_platform_ipis);
> -		seq_puts(p, "  Platform interrupts\n");
> -	}
> +	ISS(APIC_TIMER,			"LOC", " Local timer interrupts\n"),
> +	ISS(SPURIOUS,			"SPU", " Spurious interrupts\n"),
> +	ISS(APIC_PERF,			"PMI", " Performance monitoring interrupts\n"),
> +	ISS(IRQ_WORK,			"IWI", " IRQ work interrupts\n"),
> +	ISS(ICR_READ_RETRY,		"RTR", " APIC ICR read retries\n"),
> +	ISS(X86_PLATFORM_IPI,		"PLT", " Platform interrupts\n"),
>  #endif
>  #ifdef CONFIG_SMP
> -	seq_printf(p, "%*s:", prec, "RES");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_resched_count);
> -	seq_puts(p, "  Rescheduling interrupts\n");
> -	seq_printf(p, "%*s:", prec, "CAL");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_call_count);
> -	seq_puts(p, "  Function call interrupts\n");
> -	seq_printf(p, "%*s:", prec, "TLB");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_tlb_count);
> -	seq_puts(p, "  TLB shootdowns\n");
> +	ISS(RESCHEDULE,			"RES", " Rescheduling interrupts\n"),
> +	ISS(CALL_FUNCTION,		"CAL", " Function call interrupts\n"),
> +	ISS(TLB,			"TLB", " TLB shootdowns\n"),
>  #endif
>  #ifdef CONFIG_X86_THERMAL_VECTOR
> -	seq_printf(p, "%*s:", prec, "TRM");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_thermal_count);
> -	seq_puts(p, "  Thermal event interrupts\n");
> +	ISS(THERMAL_APIC,		"TRM", " Thermal event interrupt\n"),
>  #endif
>  #ifdef CONFIG_X86_MCE_THRESHOLD
> -	seq_printf(p, "%*s:", prec, "THR");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_threshold_count);
> -	seq_puts(p, "  Threshold APIC interrupts\n");
> +	ISS(THRESHOLD_APIC,		"THR", " Threshold APIC interrupts\n"),
>  #endif
>  #ifdef CONFIG_X86_MCE_AMD
> -	seq_printf(p, "%*s:", prec, "DFR");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->irq_deferred_error_count);
> -	seq_puts(p, "  Deferred Error APIC interrupts\n");
> +	ISS(DEFERRED_ERROR,		"DFR", " Deferred Error APIC interrupts\n"),
>  #endif
>  #ifdef CONFIG_X86_MCE
> -	seq_printf(p, "%*s:", prec, "MCE");
> -	for_each_online_cpu(j)
> -		put_decimal(p, per_cpu(mce_exception_count, j));
> -	seq_puts(p, "  Machine check exceptions\n");
> -	seq_printf(p, "%*s:", prec, "MCP");
> -	for_each_online_cpu(j)
> -		put_decimal(p, per_cpu(mce_poll_count, j));
> -	seq_puts(p, "  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
> -	if (test_bit(HYPERVISOR_CALLBACK_VECTOR, system_vectors)) {
> -		seq_printf(p, "%*s:", prec, "HYP");
> -		for_each_online_cpu(j)
> -			put_decimal(p, irq_stats(j)->irq_hv_callback_count);
> -		seq_puts(p, "  Hypervisor callback interrupts\n");
> -	}
> +	ITS(HYPERVISOR_CALLBACK,	"HYP", " Hypervisor callback interrupts\n"),
>  #endif
>  #if IS_ENABLED(CONFIG_HYPERV)
> -	if (test_bit(HYPERV_REENLIGHTENMENT_VECTOR, system_vectors)) {
> -		seq_printf(p, "%*s:", prec, "HRE");
> -		for_each_online_cpu(j)
> -			put_decimal(p,
> -				    irq_stats(j)->irq_hv_reenlightenment_count);
> -		seq_puts(p, "  Hyper-V reenlightenment interrupts\n");
> -	}
> -	if (test_bit(HYPERV_STIMER0_VECTOR, system_vectors)) {
> -		seq_printf(p, "%*s:", prec, "HVS");
> -		for_each_online_cpu(j)
> -			put_decimal(p, irq_stats(j)->hyperv_stimer0_count);
> -		seq_puts(p, "  Hyper-V stimer0 interrupts\n");
> -	}
> -#endif
> -	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
> -#if defined(CONFIG_X86_IO_APIC)
> -	seq_printf(p, "%*s: %10u\n", prec, "MIS", atomic_read(&irq_mis_count));
> +	ITS(HYPERV_REENLIGHTMENT,	"HRE", " Hyper-V reenlightment interrupts\n"),

s/HYPERV_REENLIGHTMENT/HYPERV_REENLIGHTENMENT/   (causes compile error)
s/reenlightment/reenlightenment/

> +	ITS(HYPERV_STIMER0,		"HVS", " Hyper-V stimer0 interrupts\n"),
>  #endif
>  #if IS_ENABLED(CONFIG_KVM)
> -	seq_printf(p, "%*s:", prec, "PIN");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->kvm_posted_intr_ipis);
> -	seq_puts(p, "  Posted-interrupt notification event\n");
> -
> -	seq_printf(p, "%*s:", prec, "NPI");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->kvm_posted_intr_nested_ipis);
> -	seq_puts(p, "  Nested posted-interrupt event\n");
> -
> -	seq_printf(p, "%*s:", prec, "PIW");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->kvm_posted_intr_wakeup_ipis);
> -	seq_puts(p, "  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
> -	seq_printf(p, "%*s:", prec, "VPMI");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->perf_guest_mediated_pmis);
> -	seq_puts(p, " Perf Guest Mediated PMI\n");
> +	ISS(PERF_GUEST_MEDIATED_PMI,	"VPMI", " Perf Guest Mediated PMI\n"),
>  #endif
>  #ifdef CONFIG_X86_POSTED_MSI
> -	seq_printf(p, "%*s:", prec, "PMN");
> -	for_each_online_cpu(j)
> -		put_decimal(p, irq_stats(j)->posted_msi_notification_count);
> -	seq_puts(p, "  Posted MSI notification event\n");
> +	ISS(POSTED_MSI_NOTIFICATION,	"PMN", " Posted MSI notification event\n"),
>  #endif
> +};