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perfcounters: throttle on too high IRQ rates 

Starting kerneltop with only -c 100 seems to be a bad idea, it can
easily lock the system due to perfcounter IRQ overload.

So add throttling: if a new IRQ arrives in a shorter than
PERFMON_MIN_PERIOD_NS time, turn off perfcounters and untrottle them
from the next timer tick.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Galbraith 2009-01-23 10:13:01 +01:00 committed by Ingo Molnar
parent 05e3423c85
commit 1b023a96d9
3 changed files with 38 additions and 6 deletions
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2
arch/x86/kernel/apic.c
View File

@ -781,6 +781,8 @@ static void local_apic_timer_interrupt(void)
inc_irq_stat(apic_timer_irqs);
evt->event_handler(evt);
perf_counter_unthrottle();
}
/*

38
arch/x86/kernel/cpu/perf_counter.c
View File

@ -33,6 +33,9 @@ static int nr_counters_fixed __read_mostly;
struct cpu_hw_counters {
struct perf_counter *counters[X86_PMC_IDX_MAX];
unsigned long used[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
u64 last_interrupt;
u64 global_enable;
int throttled;
};
/*
@ -474,16 +477,19 @@ perf_handle_group(struct perf_counter *sibling, u64 *status, u64 *overflown)
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, now;
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);
now = sched_clock();
if (now - cpuc->last_interrupt < PERFMON_MIN_PERIOD_NS)
cpuc->throttled = 1;
cpuc->last_interrupt = now;
rdmsrl(MSR_CORE_PERF_GLOBAL_STATUS, status);
if (!status)
@ -533,9 +539,29 @@ 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->throttled)
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable);
}
void perf_counter_unthrottle(void)
{
struct cpu_hw_counters *cpuc;
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->throttled) {
if (printk_ratelimit())
printk(KERN_WARNING "PERFMON: max event frequency exceeded!\n");
wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, cpuc->global_enable);
cpuc->throttled = 0;
}
}
void smp_perf_counter_interrupt(struct pt_regs *regs)

4
include/linux/perf_counter.h
View File

@ -254,6 +254,7 @@ extern void perf_counter_init_task(struct task_struct *child);
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);
@ -270,6 +271,8 @@ static inline int is_software_counter(struct perf_counter *counter)
return !counter->hw_event.raw && counter->hw_event.type < 0;
}
#define PERFMON_MIN_PERIOD_NS 10000
#else
static inline void
perf_counter_task_sched_in(struct task_struct *task, int cpu) { }
@ -281,6 +284,7 @@ static inline void perf_counter_init_task(struct task_struct *child) { }
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; }