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authorVineet Gupta <vgupta@synopsys.com>2015-10-08 22:17:48 +0530
committerVineet Gupta <vgupta@synopsys.com>2017-11-21 15:20:55 -0800
commit5b9027d6d044d4917992119d184ab0bb616489cc (patch)
tree80b05c4295140b9d1828c1fb0475c3d5bd04f214 /arch/arc
parent4d431290402c8d867af7ba45ee75407d68748c4a (diff)
downloadlinux-5b9027d6d044d4917992119d184ab0bb616489cc.tar.bz2
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) <peterz@infradead.org> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/kernel/perf_event.c16
1 files changed, 7 insertions, 9 deletions
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);