Messages in this thread Patch in this message | | | From | Vineet Gupta <> | Subject | [PATCH 5/8] ARCv2: perf: set usable max period as a half of real max period | Date | Tue, 9 Jun 2015 17:49:29 +0530 |
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From: Alexey Brodkin <abrodkin@synopsys.com>
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@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com> --- 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 4e3211948467..a7b4e4826533 100644 --- a/arch/arc/kernel/perf_event.c +++ b/arch/arc/kernel/perf_event.c @@ -491,7 +491,7 @@ 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, -- 1.9.1
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