[PATCH 05/15] perf_counter: x86: self-IPI for pending work

From: Peter Zijlstra
Date: Mon Apr 06 2009 - 05:49:19 EST

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Implement set_perf_counter_pending() with a self-IPI so that it will
run ASAP in a usable context.

For now use a second IRQ vector, because the primary vector pokes
the apic in funny ways that seem to confuse things.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
arch/x86/include/asm/entry_arch.h | 1 +
arch/x86/include/asm/hardirq.h | 1 +
arch/x86/include/asm/hw_irq.h | 1 +
arch/x86/include/asm/irq_vectors.h | 5 +++++
arch/x86/include/asm/perf_counter.h | 3 ++-
arch/x86/kernel/cpu/perf_counter.c | 14 ++++++++++++++
arch/x86/kernel/entry_64.S | 2 ++
arch/x86/kernel/irq.c | 5 +++++
arch/x86/kernel/irqinit_32.c | 1 +
arch/x86/kernel/irqinit_64.c | 1 +
10 files changed, 33 insertions(+), 1 deletion(-)

Index: linux-2.6/arch/x86/include/asm/entry_arch.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/entry_arch.h
+++ linux-2.6/arch/x86/include/asm/entry_arch.h
@@ -50,6 +50,7 @@ BUILD_INTERRUPT(spurious_interrupt,SPURI

#ifdef CONFIG_PERF_COUNTERS
BUILD_INTERRUPT(perf_counter_interrupt, LOCAL_PERF_VECTOR)
+BUILD_INTERRUPT(perf_pending_interrupt, LOCAL_PENDING_VECTOR)
#endif

#ifdef CONFIG_X86_MCE_P4THERMAL
Index: linux-2.6/arch/x86/include/asm/hardirq.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/hardirq.h
+++ linux-2.6/arch/x86/include/asm/hardirq.h
@@ -14,6 +14,7 @@ typedef struct {
#endif
unsigned int generic_irqs; /* arch dependent */
unsigned int apic_perf_irqs;
+ unsigned int apic_pending_irqs;
#ifdef CONFIG_SMP
unsigned int irq_resched_count;
unsigned int irq_call_count;
Index: linux-2.6/arch/x86/include/asm/hw_irq.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/hw_irq.h
+++ linux-2.6/arch/x86/include/asm/hw_irq.h
@@ -30,6 +30,7 @@ extern void apic_timer_interrupt(void);
extern void generic_interrupt(void);
extern void error_interrupt(void);
extern void perf_counter_interrupt(void);
+extern void perf_pending_interrupt(void);

extern void spurious_interrupt(void);
extern void thermal_interrupt(void);
Index: linux-2.6/arch/x86/include/asm/irq_vectors.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/irq_vectors.h
+++ linux-2.6/arch/x86/include/asm/irq_vectors.h
@@ -117,6 +117,11 @@
#define GENERIC_INTERRUPT_VECTOR 0xed

/*
+ * Performance monitoring pending work vector:
+ */
+#define LOCAL_PENDING_VECTOR 0xec
+
+/*
* First APIC vector available to drivers: (vectors 0x30-0xee) we
* start at 0x31(0x41) to spread out vectors evenly between priority
* levels. (0x80 is the syscall vector)
Index: linux-2.6/arch/x86/include/asm/perf_counter.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/perf_counter.h
+++ linux-2.6/arch/x86/include/asm/perf_counter.h
@@ -84,7 +84,8 @@ union cpuid10_edx {
#define MSR_ARCH_PERFMON_FIXED_CTR2 0x30b
#define X86_PMC_IDX_FIXED_BUS_CYCLES (X86_PMC_IDX_FIXED + 2)

-#define set_perf_counter_pending() do { } while (0)
+extern void set_perf_counter_pending(void);
+
#define clear_perf_counter_pending() do { } while (0)
#define test_perf_counter_pending() (0)

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
@@ -849,6 +849,20 @@ void smp_perf_counter_interrupt(struct p
irq_exit();
}

+void smp_perf_pending_interrupt(struct pt_regs *regs)
+{
+ irq_enter();
+ ack_APIC_irq();
+ inc_irq_stat(apic_pending_irqs);
+ perf_counter_do_pending();
+ irq_exit();
+}
+
+void set_perf_counter_pending(void)
+{
+ apic->send_IPI_self(LOCAL_PENDING_VECTOR);
+}
+
void perf_counters_lapic_init(int nmi)
{
u32 apic_val;
Index: linux-2.6/arch/x86/kernel/entry_64.S
===================================================================
--- linux-2.6.orig/arch/x86/kernel/entry_64.S
+++ linux-2.6/arch/x86/kernel/entry_64.S
@@ -1028,6 +1028,8 @@ apicinterrupt SPURIOUS_APIC_VECTOR \
#ifdef CONFIG_PERF_COUNTERS
apicinterrupt LOCAL_PERF_VECTOR \
perf_counter_interrupt smp_perf_counter_interrupt
+apicinterrupt LOCAL_PENDING_VECTOR \
+ perf_pending_interrupt smp_perf_pending_interrupt
#endif

/*
Index: linux-2.6/arch/x86/kernel/irq.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/irq.c
+++ linux-2.6/arch/x86/kernel/irq.c
@@ -67,6 +67,10 @@ static int show_other_interrupts(struct
for_each_online_cpu(j)
seq_printf(p, "%10u ", irq_stats(j)->apic_perf_irqs);
seq_printf(p, " Performance counter interrupts\n");
+ seq_printf(p, "PND: ");
+ for_each_online_cpu(j)
+ seq_printf(p, "%10u ", irq_stats(j)->apic_pending_irqs);
+ seq_printf(p, " Performance pending work\n");
#endif
if (generic_interrupt_extension) {
seq_printf(p, "PLT: ");
@@ -171,6 +175,7 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
sum += irq_stats(cpu)->apic_timer_irqs;
sum += irq_stats(cpu)->irq_spurious_count;
sum += irq_stats(cpu)->apic_perf_irqs;
+ sum += irq_stats(cpu)->apic_pending_irqs;
#endif
if (generic_interrupt_extension)
sum += irq_stats(cpu)->generic_irqs;
Index: linux-2.6/arch/x86/kernel/irqinit_32.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/irqinit_32.c
+++ linux-2.6/arch/x86/kernel/irqinit_32.c
@@ -166,6 +166,7 @@ static void __init apic_intr_init(void)
alloc_intr_gate(ERROR_APIC_VECTOR, error_interrupt);
# ifdef CONFIG_PERF_COUNTERS
alloc_intr_gate(LOCAL_PERF_VECTOR, perf_counter_interrupt);
+ alloc_intr_gate(LOCAL_PENDING_VECTOR, perf_pending_interrupt);
# endif

# ifdef CONFIG_X86_MCE_P4THERMAL
Index: linux-2.6/arch/x86/kernel/irqinit_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/irqinit_64.c
+++ linux-2.6/arch/x86/kernel/irqinit_64.c
@@ -156,6 +156,7 @@ static void __init apic_intr_init(void)
/* Performance monitoring interrupt: */
#ifdef CONFIG_PERF_COUNTERS
alloc_intr_gate(LOCAL_PERF_VECTOR, perf_counter_interrupt);
+ alloc_intr_gate(LOCAL_PENDING_VECTOR, perf_pending_interrupt);
#endif
}

--

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Next message: Peter Zijlstra: "[PATCH 09/15] perf_counter: counter overflow limit"
Previous message: Peter Zijlstra: "[PATCH 13/15] perf_counter: rework the task clock software counter"
In reply to: Ingo Molnar: "[tip:perfcounters/core] x86, perfcounters: add atomic64_xchg()"
Next in thread: Peter Zijlstra: "[tip:perfcounters/core] perf_counter: x86: self-IPI for pending work"
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