From f5a5a2f6e69e88647ae12da39f0ff3a510bcf0a6 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 13 May 2009 12:54:01 +0200 Subject: [PATCH] perf_counter: x86: Fix throttling If counters are disabled globally when a perfcounter IRQ/NMI hits, and if we throttle in that case, we'll promote the '0' value to the next lapic IRQ and disable all perfcounters at that point, permanently ... Fix it. [ Impact: fix hung perfcounters under load ] Acked-by: Peter Zijlstra Cc: Paul Mackerras Cc: Corey Ashford LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_counter.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 3a92a2b2a80f..88ae8cebf3c1 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -765,8 +765,13 @@ static int intel_pmu_handle_irq(struct pt_regs *regs, int nmi) /* * Restore - do not reenable when global enable is off or throttled: */ - if (++cpuc->interrupts < PERFMON_MAX_INTERRUPTS) - intel_pmu_restore_all(cpuc->throttle_ctrl); + if (cpuc->throttle_ctrl) { + if (++cpuc->interrupts < PERFMON_MAX_INTERRUPTS) { + intel_pmu_restore_all(cpuc->throttle_ctrl); + } else { + pr_info("CPU#%d: perfcounters: max interrupt rate exceeded! Throttle on.\n", smp_processor_id()); + } + } return ret; } @@ -817,11 +822,16 @@ void perf_counter_unthrottle(void) cpuc = &__get_cpu_var(cpu_hw_counters); if (cpuc->interrupts >= PERFMON_MAX_INTERRUPTS) { - if (printk_ratelimit()) - printk(KERN_WARNING "perfcounters: max interrupts exceeded!\n"); + pr_info("CPU#%d: perfcounters: throttle off.\n", smp_processor_id()); + + /* + * Clear them before re-enabling irqs/NMIs again: + */ + cpuc->interrupts = 0; hw_perf_restore(cpuc->throttle_ctrl); + } else { + cpuc->interrupts = 0; } - cpuc->interrupts = 0; } void smp_perf_counter_interrupt(struct pt_regs *regs) -- GitLab