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perfcounters: throttle on too high IRQ rates

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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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4
include/linux/perf_counter.h
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@@ -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; }