Commit a78ac325 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar

perf_counter: Generic per counter interrupt throttle

Introduce a generic per counter interrupt throttle.

This uses the perf_counter_overflow() quick disable to throttle a specific
counter when its going too fast when a pmu->unthrottle() method is provided
which can undo the quick disable.

Power needs to implement both the quick disable and the unthrottle method.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090525153931.703093461@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 48e22d56
......@@ -623,6 +623,18 @@ try_generic:
return 0;
}
static void x86_pmu_unthrottle(struct perf_counter *counter)
{
struct cpu_hw_counters *cpuc = &__get_cpu_var(cpu_hw_counters);
struct hw_perf_counter *hwc = &counter->hw;
if (WARN_ON_ONCE(hwc->idx >= X86_PMC_IDX_MAX ||
cpuc->counters[hwc->idx] != counter))
return;
x86_pmu.enable(hwc, hwc->idx);
}
void perf_counter_print_debug(void)
{
u64 ctrl, status, overflow, pmc_ctrl, pmc_count, prev_left, fixed;
......@@ -1038,6 +1050,7 @@ static const struct pmu pmu = {
.enable = x86_pmu_enable,
.disable = x86_pmu_disable,
.read = x86_pmu_read,
.unthrottle = x86_pmu_unthrottle,
};
const struct pmu *hw_perf_counter_init(struct perf_counter *counter)
......
......@@ -266,6 +266,15 @@ enum perf_event_type {
*/
PERF_EVENT_PERIOD = 4,
/*
* struct {
* struct perf_event_header header;
* u64 time;
* };
*/
PERF_EVENT_THROTTLE = 5,
PERF_EVENT_UNTHROTTLE = 6,
/*
* When header.misc & PERF_EVENT_MISC_OVERFLOW the event_type field
* will be PERF_RECORD_*
......@@ -367,6 +376,7 @@ struct pmu {
int (*enable) (struct perf_counter *counter);
void (*disable) (struct perf_counter *counter);
void (*read) (struct perf_counter *counter);
void (*unthrottle) (struct perf_counter *counter);
};
/**
......@@ -613,6 +623,7 @@ extern struct perf_callchain_entry *perf_callchain(struct pt_regs *regs);
extern int sysctl_perf_counter_priv;
extern int sysctl_perf_counter_mlock;
extern int sysctl_perf_counter_limit;
extern void perf_counter_init(void);
......
......@@ -46,6 +46,7 @@ static atomic_t nr_comm_tracking __read_mostly;
int sysctl_perf_counter_priv __read_mostly; /* do we need to be privileged */
int sysctl_perf_counter_mlock __read_mostly = 512; /* 'free' kb per user */
int sysctl_perf_counter_limit __read_mostly = 100000; /* max NMIs per second */
/*
* Lock for (sysadmin-configurable) counter reservations:
......@@ -1066,12 +1067,15 @@ static void perf_counter_cpu_sched_in(struct perf_cpu_context *cpuctx, int cpu)
__perf_counter_sched_in(ctx, cpuctx, cpu);
}
#define MAX_INTERRUPTS (~0ULL)
static void perf_log_throttle(struct perf_counter *counter, int enable);
static void perf_log_period(struct perf_counter *counter, u64 period);
static void perf_adjust_freq(struct perf_counter_context *ctx)
{
struct perf_counter *counter;
u64 irq_period;
u64 interrupts, irq_period;
u64 events, period;
s64 delta;
......@@ -1080,10 +1084,19 @@ static void perf_adjust_freq(struct perf_counter_context *ctx)
if (counter->state != PERF_COUNTER_STATE_ACTIVE)
continue;
interrupts = counter->hw.interrupts;
counter->hw.interrupts = 0;
if (interrupts == MAX_INTERRUPTS) {
perf_log_throttle(counter, 1);
counter->pmu->unthrottle(counter);
interrupts = 2*sysctl_perf_counter_limit/HZ;
}
if (!counter->hw_event.freq || !counter->hw_event.irq_freq)
continue;
events = HZ * counter->hw.interrupts * counter->hw.irq_period;
events = HZ * interrupts * counter->hw.irq_period;
period = div64_u64(events, counter->hw_event.irq_freq);
delta = (s64)(1 + period - counter->hw.irq_period);
......@@ -1097,7 +1110,6 @@ static void perf_adjust_freq(struct perf_counter_context *ctx)
perf_log_period(counter, irq_period);
counter->hw.irq_period = irq_period;
counter->hw.interrupts = 0;
}
spin_unlock(&ctx->lock);
}
......@@ -2543,6 +2555,35 @@ static void perf_log_period(struct perf_counter *counter, u64 period)
perf_output_end(&handle);
}
/*
* IRQ throttle logging
*/
static void perf_log_throttle(struct perf_counter *counter, int enable)
{
struct perf_output_handle handle;
int ret;
struct {
struct perf_event_header header;
u64 time;
} throttle_event = {
.header = {
.type = PERF_EVENT_THROTTLE + 1,
.misc = 0,
.size = sizeof(throttle_event),
},
.time = sched_clock(),
};
ret = perf_output_begin(&handle, counter, sizeof(throttle_event), 0, 0);
if (ret)
return;
perf_output_put(&handle, throttle_event);
perf_output_end(&handle);
}
/*
* Generic counter overflow handling.
*/
......@@ -2551,9 +2592,19 @@ int perf_counter_overflow(struct perf_counter *counter,
int nmi, struct pt_regs *regs, u64 addr)
{
int events = atomic_read(&counter->event_limit);
int throttle = counter->pmu->unthrottle != NULL;
int ret = 0;
counter->hw.interrupts++;
if (!throttle) {
counter->hw.interrupts++;
} else if (counter->hw.interrupts != MAX_INTERRUPTS) {
counter->hw.interrupts++;
if (HZ*counter->hw.interrupts > (u64)sysctl_perf_counter_limit) {
counter->hw.interrupts = MAX_INTERRUPTS;
perf_log_throttle(counter, 0);
ret = 1;
}
}
/*
* XXX event_limit might not quite work as expected on inherited
......
......@@ -930,6 +930,14 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
{
.ctl_name = CTL_UNNUMBERED,
.procname = "perf_counter_int_limit",
.data = &sysctl_perf_counter_limit,
.maxlen = sizeof(sysctl_perf_counter_limit),
.mode = 0644,
.proc_handler = &proc_dointvec,
},
#endif
/*
* NOTE: do not add new entries to this table unless you have read
......
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