Overflow interrupt happens when counter reaches a limit which we set as a maximum value of the counter. But for better precision counter continues registration of assigned events even after reaching pre-defined limit. To not really overlap we leave half of the counter values free. Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx> --- No changes since v1. arch/arc/kernel/perf_event.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arc/kernel/perf_event.c b/arch/arc/kernel/perf_event.c index 1a9f922..81847ef 100644 --- a/arch/arc/kernel/perf_event.c +++ b/arch/arc/kernel/perf_event.c @@ -459,7 +459,7 @@ static int arc_pmu_device_probe(struct platform_device *pdev) arc_pmu->n_counters = pct_bcr.c; counter_size = 32 + (pct_bcr.s << 4); - arc_pmu->max_period = (1ULL << counter_size) - 1ULL; + arc_pmu->max_period = (1ULL << counter_size) / 2 - 1ULL; pr_info("ARC perf\t: %d counters (%d bits), %d conditions%s\n", arc_pmu->n_counters, counter_size, cc_bcr.c, -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html