From 8a7b8cb91f26a671f22cedc7fd54508667f2d9b9 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Tue, 26 May 2009 16:27:59 +1000 Subject: perf_counter: powerpc: Implement interrupt throttling This implements interrupt throttling on powerpc. Since we don't have individual count enable/disable or interrupt enable/disable controls per counter, this simply sets the hardware counter to 0, meaning that it will not interrupt again until it has counted 2^31 counts, which will take at least 2^30 cycles assuming a maximum of 2 counts per cycle. Also, we set counter->hw.period_left to the maximum possible value (2^63 - 1), so we won't report overflows for this counter for the forseeable future. The unthrottle operation restores counter->hw.period_left and the hardware counter so that we will once again report a counter overflow after counter->hw.irq_period counts. [ Impact: new perfcounters robustness feature on PowerPC ] Signed-off-by: Paul Mackerras Cc: Peter Zijlstra Cc: Corey Ashford LKML-Reference: <18971.35823.643362.446774@cargo.ozlabs.ibm.com> Signed-off-by: Ingo Molnar --- arch/powerpc/kernel/perf_counter.c | 48 ++++++++++++++++++++++++++++++++++---- 1 file changed, 43 insertions(+), 5 deletions(-) (limited to 'arch/powerpc') diff --git a/arch/powerpc/kernel/perf_counter.c b/arch/powerpc/kernel/perf_counter.c index fe21b2440f2..f96d55f55bd 100644 --- a/arch/powerpc/kernel/perf_counter.c +++ b/arch/powerpc/kernel/perf_counter.c @@ -740,10 +740,37 @@ static void power_pmu_disable(struct perf_counter *counter) local_irq_restore(flags); } +/* + * Re-enable interrupts on a counter after they were throttled + * because they were coming too fast. + */ +static void power_pmu_unthrottle(struct perf_counter *counter) +{ + s64 val, left; + unsigned long flags; + + if (!counter->hw.idx || !counter->hw.irq_period) + return; + local_irq_save(flags); + perf_disable(); + power_pmu_read(counter); + left = counter->hw.irq_period; + val = 0; + if (left < 0x80000000L) + val = 0x80000000L - left; + write_pmc(counter->hw.idx, val); + atomic64_set(&counter->hw.prev_count, val); + atomic64_set(&counter->hw.period_left, left); + perf_counter_update_userpage(counter); + perf_enable(); + local_irq_restore(flags); +} + struct pmu power_pmu = { .enable = power_pmu_enable, .disable = power_pmu_disable, .read = power_pmu_read, + .unthrottle = power_pmu_unthrottle, }; /* @@ -957,10 +984,6 @@ static void record_and_restart(struct perf_counter *counter, long val, if (left < 0x80000000L) val = 0x80000000L - left; } - write_pmc(counter->hw.idx, val); - atomic64_set(&counter->hw.prev_count, val); - atomic64_set(&counter->hw.period_left, left); - perf_counter_update_userpage(counter); /* * Finally record data if requested. @@ -983,8 +1006,23 @@ static void record_and_restart(struct perf_counter *counter, long val, if (!(mmcra & MMCRA_SAMPLE_ENABLE) || (mmcra & sdsync)) addr = mfspr(SPRN_SDAR); } - perf_counter_overflow(counter, nmi, regs, addr); + if (perf_counter_overflow(counter, nmi, regs, addr)) { + /* + * Interrupts are coming too fast - throttle them + * by setting the counter to 0, so it will be + * at least 2^30 cycles until the next interrupt + * (assuming each counter counts at most 2 counts + * per cycle). + */ + val = 0; + left = ~0ULL >> 1; + } } + + write_pmc(counter->hw.idx, val); + atomic64_set(&counter->hw.prev_count, val); + atomic64_set(&counter->hw.period_left, left); + perf_counter_update_userpage(counter); } /* -- cgit v1.2.3