Hi Marc, On Tue, 1 Sep 2020 at 16:44, Marc Zyngier <m...@kernel.org> wrote: > > In order to deal with IPIs as normal interrupts, let's add > a new way to register them with the architecture code. > > set_smp_ipi_range() takes a range of interrupts, and allows > the arch code to request them as if the were normal interrupts. > A standard handler is then called by the core IRQ code to deal > with the IPI. > > This means that we don't need to call irq_enter/irq_exit, and > that we don't need to deal with set_irq_regs either. So let's > move the dispatcher into its own function, and leave handle_IPI() > as a compatibility function. > > On the sending side, let's make use of ipi_send_mask, which > already exists for this purpose. > > One of the major difference is that we end up, in some cases > (such as when performing IRQ time accounting on the scheduler > IPI), end up with nested irq_enter()/irq_exit() pairs. > Other than the (relatively small) overhead, there should be > no consequences to it (these pairs are designed to nest > correctly, and the accounting shouldn't be off).
While rebasing on mainline, I have faced a performance regression for the benchmark: perf bench sched pipe on my arm64 dual quad core (hikey) and my 2 nodes x 112 CPUS (thx2) The regression comes from: commit: d3afc7f12987 ("arm64: Allow IPIs to be handled as normal interrupts") v5.9 + this patch hikey : 48818(+/- 0.31) 37503(+/- 0.15%) -23.2% thx2 : 132410(+/- 1.72) 122646(+/- 1.92%) -7.4% By + this patch, I mean merging branch from this patch. Whereas merging the previous: commit: 83cfac95c018 ("genirq: Allow interrupts to be excluded from /proc/interrupts") It doesn't show any regression Vincent > > Reviewed-by: Valentin Schneider <valentin.schnei...@arm.com> > Signed-off-by: Marc Zyngier <m...@kernel.org> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/smp.h | 5 ++ > arch/arm64/kernel/smp.c | 93 +++++++++++++++++++++++++++++++----- > 3 files changed, 87 insertions(+), 12 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 6d232837cbee..d0fdbe5fb32f 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -106,6 +106,7 @@ config ARM64 > select GENERIC_CPU_VULNERABILITIES > select GENERIC_EARLY_IOREMAP > select GENERIC_IDLE_POLL_SETUP > + select GENERIC_IRQ_IPI > select GENERIC_IRQ_MULTI_HANDLER > select GENERIC_IRQ_PROBE > select GENERIC_IRQ_SHOW > diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h > index 0eadbf933e35..57c5db15f6b7 100644 > --- a/arch/arm64/include/asm/smp.h > +++ b/arch/arm64/include/asm/smp.h > @@ -78,6 +78,11 @@ extern void set_smp_cross_call(void (*)(const struct > cpumask *, unsigned int)); > > extern void (*__smp_cross_call)(const struct cpumask *, unsigned int); > > +/* > + * Register IPI interrupts with the arch SMP code > + */ > +extern void set_smp_ipi_range(int ipi_base, int nr_ipi); > + > /* > * Called from the secondary holding pen, this is the secondary CPU entry > point. > */ > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 355ee9eed4dd..00c9db1b61b5 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -75,6 +75,13 @@ enum ipi_msg_type { > IPI_WAKEUP > }; > > +static int ipi_irq_base __read_mostly; > +static int nr_ipi __read_mostly = NR_IPI; > +static struct irq_desc *ipi_desc[NR_IPI] __read_mostly; > + > +static void ipi_setup(int cpu); > +static void ipi_teardown(int cpu); > + > #ifdef CONFIG_HOTPLUG_CPU > static int op_cpu_kill(unsigned int cpu); > #else > @@ -237,6 +244,8 @@ asmlinkage notrace void secondary_start_kernel(void) > */ > notify_cpu_starting(cpu); > > + ipi_setup(cpu); > + > store_cpu_topology(cpu); > numa_add_cpu(cpu); > > @@ -302,6 +311,7 @@ int __cpu_disable(void) > * and we must not schedule until we're ready to give up the cpu. > */ > set_cpu_online(cpu, false); > + ipi_teardown(cpu); > > /* > * OK - migrate IRQs away from this CPU > @@ -890,10 +900,9 @@ static void ipi_cpu_crash_stop(unsigned int cpu, struct > pt_regs *regs) > /* > * Main handler for inter-processor interrupts > */ > -void handle_IPI(int ipinr, struct pt_regs *regs) > +static void do_handle_IPI(int ipinr) > { > unsigned int cpu = smp_processor_id(); > - struct pt_regs *old_regs = set_irq_regs(regs); > > if ((unsigned)ipinr < NR_IPI) { > trace_ipi_entry_rcuidle(ipi_types[ipinr]); > @@ -906,21 +915,16 @@ void handle_IPI(int ipinr, struct pt_regs *regs) > break; > > case IPI_CALL_FUNC: > - irq_enter(); > generic_smp_call_function_interrupt(); > - irq_exit(); > break; > > case IPI_CPU_STOP: > - irq_enter(); > local_cpu_stop(); > - irq_exit(); > break; > > case IPI_CPU_CRASH_STOP: > if (IS_ENABLED(CONFIG_KEXEC_CORE)) { > - irq_enter(); > - ipi_cpu_crash_stop(cpu, regs); > + ipi_cpu_crash_stop(cpu, get_irq_regs()); > > unreachable(); > } > @@ -928,17 +932,13 @@ void handle_IPI(int ipinr, struct pt_regs *regs) > > #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST > case IPI_TIMER: > - irq_enter(); > tick_receive_broadcast(); > - irq_exit(); > break; > #endif > > #ifdef CONFIG_IRQ_WORK > case IPI_IRQ_WORK: > - irq_enter(); > irq_work_run(); > - irq_exit(); > break; > #endif > > @@ -957,9 +957,78 @@ void handle_IPI(int ipinr, struct pt_regs *regs) > > if ((unsigned)ipinr < NR_IPI) > trace_ipi_exit_rcuidle(ipi_types[ipinr]); > +} > + > +/* Legacy version, should go away once all irqchips have been converted */ > +void handle_IPI(int ipinr, struct pt_regs *regs) > +{ > + struct pt_regs *old_regs = set_irq_regs(regs); > + > + irq_enter(); > + do_handle_IPI(ipinr); > + irq_exit(); > + > set_irq_regs(old_regs); > } > > +static irqreturn_t ipi_handler(int irq, void *data) > +{ > + do_handle_IPI(irq - ipi_irq_base); > + return IRQ_HANDLED; > +} > + > +static void ipi_send(const struct cpumask *target, unsigned int ipi) > +{ > + __ipi_send_mask(ipi_desc[ipi], target); > +} > + > +static void ipi_setup(int cpu) > +{ > + int i; > + > + if (!ipi_irq_base) > + return; > + > + for (i = 0; i < nr_ipi; i++) > + enable_percpu_irq(ipi_irq_base + i, 0); > +} > + > +static void ipi_teardown(int cpu) > +{ > + int i; > + > + if (!ipi_irq_base) > + return; > + > + for (i = 0; i < nr_ipi; i++) > + disable_percpu_irq(ipi_irq_base + i); > +} > + > +void __init set_smp_ipi_range(int ipi_base, int n) > +{ > + int i; > + > + WARN_ON(n < NR_IPI); > + nr_ipi = min(n, NR_IPI); > + > + for (i = 0; i < nr_ipi; i++) { > + int err; > + > + err = request_percpu_irq(ipi_base + i, ipi_handler, > + "IPI", &irq_stat); > + WARN_ON(err); > + > + ipi_desc[i] = irq_to_desc(ipi_base + i); > + irq_set_status_flags(ipi_base + i, IRQ_HIDDEN); > + } > + > + ipi_irq_base = ipi_base; > + __smp_cross_call = ipi_send; > + > + /* Setup the boot CPU immediately */ > + ipi_setup(smp_processor_id()); > +} > + > void smp_send_reschedule(int cpu) > { > smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE); > -- > 2.27.0 >