[patch V2 21/28] x86/perf/intel/rapl: Calculate timing once

From: Thomas Gleixner
Date: Mon Feb 22 2016 - 06:08:24 EST


No point in doing the same calculation over and over. Do it once in
rapl_check_hw_unit().

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/perf_event_intel_rapl.c | 39 ++++++++++++----------------
1 file changed, 18 insertions(+), 21 deletions(-)

Index: b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
===================================================================
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -129,6 +129,7 @@ static int rapl_hw_unit[NR_RAPL_DOMAINS]
static struct pmu rapl_pmu_class;
static cpumask_t rapl_cpu_mask;
static int rapl_cntr_mask;
+static u64 rapl_timer_ms;

static DEFINE_PER_CPU(struct rapl_pmu *, rapl_pmu);
static DEFINE_PER_CPU(struct rapl_pmu *, rapl_pmu_to_free);
@@ -558,7 +559,6 @@ static int rapl_cpu_prepare(int cpu)
{
struct rapl_pmu *pmu = per_cpu(rapl_pmu, cpu);
int phys_id = topology_physical_package_id(cpu);
- u64 ms;

if (pmu)
return 0;
@@ -575,19 +575,7 @@ static int rapl_cpu_prepare(int cpu)

pmu->pmu = &rapl_pmu_class;

- /*
- * use reference of 200W for scaling the timeout
- * to avoid missing counter overflows.
- * 200W = 200 Joules/sec
- * divide interval by 2 to avoid lockstep (2 * 100)
- * if hw unit is 32, then we use 2 ms 1/200/2
- */
- if (rapl_hw_unit[0] < 32)
- ms = (1000 / (2 * 100)) * (1ULL << (32 - rapl_hw_unit[0] - 1));
- else
- ms = 2;
-
- pmu->timer_interval = ms_to_ktime(ms);
+ pmu->timer_interval = ms_to_ktime(rapl_timer_ms);

rapl_hrtimer_init(pmu);

@@ -676,6 +664,19 @@ static int rapl_check_hw_unit(void (*qui
/* Apply cpu model quirk */
if (quirk)
quirk();
+
+ /*
+ * Calculate the timer rate:
+ * Use reference of 200W for scaling the timeout to avoid counter
+ * overflows. 200W = 200 Joules/sec
+ * Divide interval by 2 to avoid lockstep (2 * 100)
+ * if hw unit is 32, then we use 2 ms 1/200/2
+ */
+ rapl_timer_ms = 2;
+ if (rapl_hw_unit[0] < 32) {
+ rapl_timer_ms = (1000 / (2 * 100));
+ rapl_timer_ms *= (1ULL << (32 - rapl_hw_unit[0] - 1));
+ }
return 0;
}

@@ -695,9 +696,7 @@ static const struct x86_cpu_id rapl_cpu_
static int __init rapl_pmu_init(void)
{
void (*quirk)(void) = NULL;
- struct rapl_pmu *pmu;
- int cpu, ret;
- int i;
+ int cpu, ret, i;

/*
* check for Intel processor family 6
@@ -758,15 +757,14 @@ static int __init rapl_pmu_init(void)
}

__perf_cpu_notifier(rapl_cpu_notifier);
-
- pmu = __this_cpu_read(rapl_pmu);
+ cpu_notifier_register_done();

pr_info("RAPL PMU detected,"
" API unit is 2^-32 Joules,"
" %d fixed counters"
" %llu ms ovfl timer\n",
hweight32(rapl_cntr_mask),
- ktime_to_ms(pmu->timer_interval));
+ rapl_timer_ms);
for (i = 0; i < NR_RAPL_DOMAINS; i++) {
if (rapl_cntr_mask & (1 << i)) {
pr_info("hw unit of domain %s 2^-%d Joules\n",
@@ -774,7 +772,6 @@ static int __init rapl_pmu_init(void)
}
}

- cpu_notifier_register_done();
return 0;

out: