From 5b9027d6d044d4917992119d184ab0bb616489cc Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Thu, 8 Oct 2015 22:17:48 +0530 Subject: ARCv2: perf: optimize given that num counters <= 32 use ffz primitive which maps to ARCv2 instruction, vs. non atomic __test_and_set_bit It is unlikely if we will even have more than 32 counters, but still add a BUILD_BUG to catch that Acked-by: Peter Zijlstra (Intel) Signed-off-by: Vineet Gupta --- arch/arc/kernel/perf_event.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) (limited to 'arch/arc') diff --git a/arch/arc/kernel/perf_event.c b/arch/arc/kernel/perf_event.c index 0eaa132a2c90..8aec462d90fb 100644 --- a/arch/arc/kernel/perf_event.c +++ b/arch/arc/kernel/perf_event.c @@ -336,15 +336,12 @@ static int arc_pmu_add(struct perf_event *event, int flags) struct hw_perf_event *hwc = &event->hw; int idx = hwc->idx; - if (__test_and_set_bit(idx, pmu_cpu->used_mask)) { - idx = find_first_zero_bit(pmu_cpu->used_mask, - arc_pmu->n_counters); - if (idx == arc_pmu->n_counters) - return -EAGAIN; - - __set_bit(idx, pmu_cpu->used_mask); - hwc->idx = idx; - } + idx = ffz(pmu_cpu->used_mask[0]); + if (idx == arc_pmu->n_counters) + return -EAGAIN; + + __set_bit(idx, pmu_cpu->used_mask); + hwc->idx = idx; write_aux_reg(ARC_REG_PCT_INDEX, idx); @@ -465,6 +462,7 @@ static int arc_pmu_device_probe(struct platform_device *pdev) pr_err("This core does not have performance counters!\n"); return -ENODEV; } + BUILD_BUG_ON(ARC_PERF_MAX_COUNTERS > 32); BUG_ON(pct_bcr.c > ARC_PERF_MAX_COUNTERS); READ_BCR(ARC_REG_CC_BUILD, cc_bcr); -- cgit v1.2.3