From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: <linux-snps-arc@lists.infradead.org>
Cc: <linux-kernel@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: [PATCH 2/4] ARCv2: perf: optimize given that num counters <= 32
Date: Tue, 7 Nov 2017 14:13:02 -0800 [thread overview]
Message-ID: <1510092784-19942-3-git-send-email-vgupta@synopsys.com> (raw)
In-Reply-To: <1510092784-19942-1-git-send-email-vgupta@synopsys.com>
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
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/kernel/perf_event.c | 16 +++++++---------
1 file 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);
--
2.7.4
next prev parent reply other threads:[~2017-11-07 22:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 22:13 [PATCH 0/4] ARC perf updates Vineet Gupta
2017-11-07 22:13 ` [PATCH 1/4] ARCv2: perf: tweak overflow interrupt Vineet Gupta
2017-11-07 22:13 ` Vineet Gupta [this message]
2017-11-07 22:13 ` [PATCH 3/4] ARC: perf: avoid vmalloc backed mmap Vineet Gupta
2017-11-07 22:13 ` [PATCH 4/4] ARCv2: entry: Reduce perf intr return path Vineet Gupta
2017-11-14 10:28 ` Peter Zijlstra
2017-11-14 23:01 ` Vineet Gupta
2017-11-15 10:18 ` Peter Zijlstra
2017-11-17 23:42 ` Vineet Gupta
2017-11-21 23:26 ` Vineet Gupta
2017-11-13 21:30 ` [PATCH 0/4] ARC perf updates Vineet Gupta
2017-11-21 22:09 ` Vineet Gupta
2017-11-21 23:13 ` Peter Zijlstra
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