diff options
| -rw-r--r-- | arch/arm/Kconfig | 10 | ||||
| -rw-r--r-- | arch/arm/kernel/entry-armv.S | 7 | ||||
| -rw-r--r-- | arch/arm/kernel/irq.c | 1 | ||||
| -rw-r--r-- | arch/arm/kernel/smp.c | 34 | ||||
| -rw-r--r-- | include/asm-arm/hardirq.h | 1 | ||||
| -rw-r--r-- | include/asm-arm/smp.h | 38 |
6 files changed, 91 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 91d5ef3397be..3bfef0934c9d 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -356,6 +356,16 @@ config HOTPLUG_CPU Say Y here to experiment with turning CPUs off and on. CPUs can be controlled through /sys/devices/system/cpu. +config LOCAL_TIMERS + bool "Use local timer interrupts" + depends on SMP && n + default y + help + Enable support for local timers on SMP platforms, rather then the + legacy IPI broadcast method. Local timers allows the system + accounting to be spread across the timer interval, preventing a + "thundering herd" at every timer tick. + config PREEMPT bool "Preemptible Kernel (EXPERIMENTAL)" depends on EXPERIMENTAL diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index a511ec5b11a3..d9fb819bf7cc 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -47,6 +47,13 @@ movne r0, sp adrne lr, 1b bne do_IPI + +#ifdef CONFIG_LOCAL_TIMERS + test_for_ltirq r0, r6, r5, lr + movne r0, sp + adrne lr, 1b + bne do_local_timer +#endif #endif .endm diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c index 6f86d0af7c56..d7099dbbb879 100644 --- a/arch/arm/kernel/irq.c +++ b/arch/arm/kernel/irq.c @@ -264,6 +264,7 @@ unlock: #endif #ifdef CONFIG_SMP show_ipi_list(p); + show_local_irqs(p); #endif seq_printf(p, "Err: %10lu\n", irq_err_count); } diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index f5fc57e0fe41..77e2e9ca89fa 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -185,6 +185,11 @@ int __cpuexit __cpu_disable(void) migrate_irqs(); /* + * Stop the local timer for this CPU. + */ + local_timer_stop(cpu); + + /* * Flush user cache and TLB mappings, and then remove this CPU * from the vm mask set of all processes. */ @@ -290,6 +295,11 @@ asmlinkage void __cpuinit secondary_start_kernel(void) cpu_set(cpu, cpu_online_map); /* + * Setup local timer for this CPU. + */ + local_timer_setup(cpu); + + /* * OK, it's off to the idle thread for us */ cpu_idle(); @@ -454,6 +464,18 @@ void show_ipi_list(struct seq_file *p) seq_putc(p, '\n'); } +void show_local_irqs(struct seq_file *p) +{ + unsigned int cpu; + + seq_printf(p, "LOC: "); + + for_each_present_cpu(cpu) + seq_printf(p, "%10u ", irq_stat[cpu].local_timer_irqs); + + seq_putc(p, '\n'); +} + static void ipi_timer(struct pt_regs *regs) { int user = user_mode(regs); @@ -464,6 +486,18 @@ static void ipi_timer(struct pt_regs *regs) irq_exit(); } +#ifdef CONFIG_LOCAL_TIMERS +asmlinkage void do_local_timer(struct pt_regs *regs) +{ + int cpu = smp_processor_id(); + + if (local_timer_ack()) { + irq_stat[cpu].local_timer_irqs++; + ipi_timer(regs); + } +} +#endif + /* * ipi_call_function - handle IPI from smp_call_function() * diff --git a/include/asm-arm/hardirq.h b/include/asm-arm/hardirq.h index e5ccb6b8ff83..1cbb173bf5b1 100644 --- a/include/asm-arm/hardirq.h +++ b/include/asm-arm/hardirq.h @@ -8,6 +8,7 @@ typedef struct { unsigned int __softirq_pending; + unsigned int local_timer_irqs; } ____cacheline_aligned irq_cpustat_t; #include <linux/irq_cpustat.h> /* Standard mappings for irq_cpustat_t above */ diff --git a/include/asm-arm/smp.h b/include/asm-arm/smp.h index 52e7c8d830b2..5a72e50ca9fc 100644 --- a/include/asm-arm/smp.h +++ b/include/asm-arm/smp.h @@ -92,4 +92,42 @@ extern void platform_cpu_die(unsigned int cpu); extern int platform_cpu_kill(unsigned int cpu); extern void platform_cpu_enable(unsigned int cpu); +#ifdef CONFIG_LOCAL_TIMERS +/* + * Setup a local timer interrupt for a CPU. + */ +extern void local_timer_setup(unsigned int cpu); + +/* + * Stop a local timer interrupt. + */ +extern void local_timer_stop(unsigned int cpu); + +/* + * Platform provides this to acknowledge a local timer IRQ + */ +extern int local_timer_ack(void); + +#else + +static inline void local_timer_setup(unsigned int cpu) +{ +} + +static inline void local_timer_stop(unsigned int cpu) +{ +} + +#endif + +/* + * show local interrupt info + */ +extern void show_local_irqs(struct seq_file *); + +/* + * Called from assembly, this is the local timer IRQ handler + */ +asmlinkage void do_local_timer(struct pt_regs *); + #endif /* ifndef __ASM_ARM_SMP_H */ |