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Subject[PATCH 2/3] perf_counter: x86: remove interrupt throttle
remove the x86 specific interrupt throttle

LKML-Reference: <new-submission>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
arch/x86/kernel/apic/apic.c | 2 -
arch/x86/kernel/cpu/perf_counter.c | 47 +++----------------------------------
include/linux/perf_counter.h | 2 -
3 files changed, 5 insertions(+), 46 deletions(-)
Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6/arch/x86/kernel/apic/apic.c
@@ -817,8 +817,6 @@ 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
@@ -719,11 +719,6 @@ static void intel_pmu_save_and_restart(s
}

/*
- * Maximum 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:
*/
@@ -775,15 +770,14 @@ again:
if (status)
goto again;

- if (++cpuc->interrupts != PERFMON_MAX_INTERRUPTS)
- perf_enable();
+ perf_enable();

return 1;
}

static int amd_pmu_handle_irq(struct pt_regs *regs, int nmi)
{
- int cpu, idx, throttle = 0, handled = 0;
+ int cpu, idx, handled = 0;
struct cpu_hw_counters *cpuc;
struct perf_counter *counter;
struct hw_perf_counter *hwc;
@@ -792,16 +786,7 @@ static int amd_pmu_handle_irq(struct pt_
cpu = smp_processor_id();
cpuc = &per_cpu(cpu_hw_counters, cpu);

- if (++cpuc->interrupts == PERFMON_MAX_INTERRUPTS) {
- throttle = 1;
- __perf_disable();
- cpuc->enabled = 0;
- barrier();
- }
-
for (idx = 0; idx < x86_pmu.num_counters; idx++) {
- int disable = 0;
-
if (!test_bit(idx, cpuc->active_mask))
continue;

@@ -809,45 +794,23 @@ static int amd_pmu_handle_irq(struct pt_
hwc = &counter->hw;

if (counter->hw_event.nmi != nmi)
- goto next;
+ continue;

val = x86_perf_counter_update(counter, hwc, idx);
if (val & (1ULL << (x86_pmu.counter_bits - 1)))
- goto next;
+ continue;

/* counter overflow */
x86_perf_counter_set_period(counter, hwc, idx);
handled = 1;
inc_irq_stat(apic_perf_irqs);
- disable = perf_counter_overflow(counter, nmi, regs, 0);
-
-next:
- if (disable || throttle)
+ if (perf_counter_overflow(counter, nmi, regs, 0))
amd_pmu_disable_counter(hwc, idx);
}

return handled;
}

-void perf_counter_unthrottle(void)
-{
- struct cpu_hw_counters *cpuc;
-
- if (!x86_pmu_initialized())
- return;
-
- cpuc = &__get_cpu_var(cpu_hw_counters);
- if (cpuc->interrupts >= PERFMON_MAX_INTERRUPTS) {
- /*
- * Clear them before re-enabling irqs/NMIs again:
- */
- cpuc->interrupts = 0;
- perf_enable();
- } else {
- cpuc->interrupts = 0;
- }
-}
-
void smp_perf_counter_interrupt(struct pt_regs *regs)
{
irq_enter();
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
@@ -570,7 +570,6 @@ extern void perf_counter_init_task(struc
extern void perf_counter_exit_task(struct task_struct *child);
extern void perf_counter_do_pending(void);
extern void perf_counter_print_debug(void);
-extern void perf_counter_unthrottle(void);
extern void __perf_disable(void);
extern bool __perf_enable(void);
extern void perf_disable(void);
@@ -635,7 +634,6 @@ static inline void perf_counter_init_tas
static inline void perf_counter_exit_task(struct task_struct *child) { }
static inline void perf_counter_do_pending(void) { }
static inline void perf_counter_print_debug(void) { }
-static inline void perf_counter_unthrottle(void) { }
static inline void perf_disable(void) { }
static inline void perf_enable(void) { }
static inline int perf_counter_task_disable(void) { return -EINVAL; }
--



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