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perf_counter: Generic per counter interrupt throttle

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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: Peter 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
2009-05-25 17:39:05 +02:00
committed by Ingo Molnar
parent 48e22d56ec
commit a78ac32587
4 changed files with 87 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

59
kernel/perf_counter.c
View File

@@ -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

8
kernel/sysctl.c
View File

@@ -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