Messages in this thread Patch in this message | | | Subject | [patch] ratelimit performance counter interrupts | From | Mike Galbraith <> | Date | Fri, 23 Jan 2009 14:07:10 +0100 |
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While fiddling around with kerneltop, I found that an unwary user can lock his box up quite thoroughly if he does something really clever like starting kerneltop with -c 100.
Ratelimit performance counter interrupts to 100KHz per CPU.
Signed-off-by: Mike Galbraith <efault@gmx.de>
--- arch/x86/kernel/apic.c | 2 + arch/x86/kernel/cpu/perf_counter.c | 43 ++++++++++++++++++++++++++++++------- include/linux/perf_counter.h | 2 + 3 files changed, 40 insertions(+), 7 deletions(-)
Index: linux-2.6/arch/x86/kernel/apic.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/apic.c +++ linux-2.6/arch/x86/kernel/apic.c @@ -781,6 +781,8 @@ static void local_apic_timer_interrupt(v inc_irq_stat(apic_timer_irqs); evt->event_handler(evt); + + perf_counter_unthrottle(); } /* Index: linux-2.6/arch/x86/kernel/cpu/perf_counter.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/cpu/perf_counter.c +++ linux-2.6/arch/x86/kernel/cpu/perf_counter.c @@ -33,6 +33,8 @@ static int nr_counters_fixed __read_most struct cpu_hw_counters { struct perf_counter *counters[X86_PMC_IDX_MAX]; unsigned long used[BITS_TO_LONGS(X86_PMC_IDX_MAX)]; + unsigned long interrupts; + u64 global_enable; }; /* @@ -468,23 +470,26 @@ perf_handle_group(struct perf_counter *s } /* + * Mamimum interrupt frequency of 100KHz per CPU + */ +#define PERFMON_MAX_INTERRUPTS 100000/HZ + +/* * This handler is triggered by the local APIC, so the APIC IRQ handling * rules apply: */ static void __smp_perf_counter_interrupt(struct pt_regs *regs, int nmi) { int bit, cpu = smp_processor_id(); - u64 ack, status, saved_global; - struct cpu_hw_counters *cpuc; + u64 ack, status; + struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu); - rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, saved_global); + rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); /* Disable counters globally */ wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0); ack_APIC_irq(); - cpuc = &per_cpu(cpu_hw_counters, cpu); - rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status); if (!status) goto out; @@ -533,9 +538,33 @@ again: goto again; out: /* - * Restore - do not reenable when global enable is off: + * Restore - do not reenable when global enable is off or throttled: */ - wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, saved_global); + if (++cpuc->interrupts < PERFMON_MAX_INTERRUPTS) + wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); +} + +void perf_counter_unthrottle(void) +{ + struct cpu_hw_counters *cpuc; + u64 global_enable; + + if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) + return; + + if (unlikely(!perf_counters_initialized)) + return; + + cpuc = &per_cpu(cpu_hw_counters, smp_processor_id()); + if (cpuc->interrupts >= PERFMON_MAX_INTERRUPTS) { + if (printk_ratelimit()) + printk(KERN_WARNING "PERFMON: max interrupts exceeded!\n"); + wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); + } + rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, global_enable); + if (unlikely(cpuc->global_enable && !global_enable)) + wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable); + cpuc->interrupts = 0; } void smp_perf_counter_interrupt(struct pt_regs *regs) Index: linux-2.6/include/linux/perf_counter.h =================================================================== --- linux-2.6.orig/include/linux/perf_counter.h +++ linux-2.6/include/linux/perf_counter.h @@ -254,6 +254,7 @@ extern void perf_counter_init_task(struc extern void perf_counter_exit_task(struct task_struct *child); extern void perf_counter_notify(struct pt_regs *regs); extern void perf_counter_print_debug(void); +extern void perf_counter_unthrottle(void); extern u64 hw_perf_save_disable(void); extern void hw_perf_restore(u64 ctrl); extern int perf_counter_task_disable(void); @@ -281,6 +282,7 @@ static inline void perf_counter_init_tas static inline void perf_counter_exit_task(struct task_struct *child) { } static inline void perf_counter_notify(struct pt_regs *regs) { } static inline void perf_counter_print_debug(void) { } +static inline void perf_counter_unthrottle(void) { } static inline void hw_perf_restore(u64 ctrl) { } static inline u64 hw_perf_save_disable(void) { return 0; } static inline int perf_counter_task_disable(void) { return -EINVAL; }
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