KT-45777: Track build time in nanoseconds instead of milliseconds

to ensure precision (otherwise, rounding errors to milliseconds may
add up and cause unexplainable gaps in the running time).

We can still use milliseconds in the final report after all the precise
sub-build-times have been aggregated.

build-common/src/org/jetbrains/kotlin/build/report/metrics/BuildMetricsReporter.kt

@@ -6,26 +6,24 @@
 package org.jetbrains.kotlin.build.report.metrics
 
 interface BuildMetricsReporter {
-    fun startMeasure(time: BuildTime, startNs: Long)
-    fun endMeasure(time: BuildTime, endNs: Long)
-    fun addTimeMetric(time: BuildTime, durationMs: Long)
+    fun startMeasure(time: BuildTime)
+    fun endMeasure(time: BuildTime)
+    fun addTimeMetricNs(time: BuildTime, durationNs: Long)
+    fun addTimeMetricMs(time: BuildTime, durationMs: Long) = addTimeMetricNs(time, durationMs * 1_000_000)
 
     fun addMetric(metric: BuildPerformanceMetric, value: Long)
 
     fun addAttribute(attribute: BuildAttribute)
 
     fun getMetrics(): BuildMetrics
-    fun addMetrics(metrics: BuildMetrics?)
+    fun addMetrics(metrics: BuildMetrics)
 }
 
 inline fun <T> BuildMetricsReporter.measure(time: BuildTime, fn: () -> T): T {
-    val start = System.nanoTime()
-    startMeasure(time, start)
-
+    startMeasure(time)
     try {
         return fn()
     } finally {
-        val end = System.nanoTime()
-        endMeasure(time, end)
+        endMeasure(time)
     }
 }

build-common/src/org/jetbrains/kotlin/build/report/metrics/BuildMetricsReporterImpl.kt

@@ -17,21 +17,21 @@ class BuildMetricsReporterImpl : BuildMetricsReporter, Serializable {
     private val myBuildMetrics = BuildPerformanceMetrics()
     private val myBuildAttributes = BuildAttributes()
 
-    override fun startMeasure(time: BuildTime, startNs: Long) {
+    override fun startMeasure(time: BuildTime) {
         if (time in myBuildTimeStartNs) {
             error("$time was restarted before it finished")
         }
-        myBuildTimeStartNs[time] = startNs
+        myBuildTimeStartNs[time] = System.nanoTime()
     }
 
-    override fun endMeasure(time: BuildTime, endNs: Long) {
+    override fun endMeasure(time: BuildTime) {
         val startNs = myBuildTimeStartNs.remove(time) ?: error("$time finished before it started")
-        val durationMs = (endNs - startNs) / 1_000_000
-        myBuildTimes.add(time, durationMs)
+        val durationNs = System.nanoTime() - startNs
+        myBuildTimes.addTimeNs(time, durationNs)
     }
 
-    override fun addTimeMetric(time: BuildTime, durationMs: Long) {
-        myBuildTimes.add(time, durationMs)
+    override fun addTimeMetricNs(time: BuildTime, durationNs: Long) {
+        myBuildTimes.addTimeNs(time, durationNs)
     }
 
     override fun addMetric(metric: BuildPerformanceMetric, value: Long) {
@@ -49,9 +49,7 @@ class BuildMetricsReporterImpl : BuildMetricsReporter, Serializable {
             buildAttributes = myBuildAttributes
         )
 
-    override fun addMetrics(metrics: BuildMetrics?) {
-        if (metrics == null) return
-
+    override fun addMetrics(metrics: BuildMetrics) {
         myBuildAttributes.addAll(metrics.buildAttributes)
         myBuildTimes.addAll(metrics.buildTimes)
         myBuildMetrics.addAll(metrics.buildPerformanceMetrics)

build-common/src/org/jetbrains/kotlin/build/report/metrics/BuildTimes.kt

@@ -9,19 +9,23 @@ import java.io.Serializable
 import java.util.*
 
 class BuildTimes : Serializable {
-    private val myBuildTimes = EnumMap<BuildTime, Long>(BuildTime::class.java)
+    private val buildTimesNs = EnumMap<BuildTime, Long>(BuildTime::class.java)
 
     fun addAll(other: BuildTimes) {
-        for ((bt, timeMs) in other.myBuildTimes) {
-            add(bt, timeMs)
+        for ((buildTime, timeNs) in other.buildTimesNs) {
+            addTimeNs(buildTime, timeNs)
         }
     }
 
-    fun add(buildTime: BuildTime, timeMs: Long) {
-        myBuildTimes[buildTime] = myBuildTimes.getOrDefault(buildTime, 0) + timeMs
+    fun addTimeNs(buildTime: BuildTime, timeNs: Long) {
+        buildTimesNs[buildTime] = buildTimesNs.getOrDefault(buildTime, 0) + timeNs
     }
 
-    fun asMap(): Map<BuildTime, Long> = myBuildTimes
+    fun addTimeMs(buildTime: BuildTime, timeMs: Long) = addTimeNs(buildTime, timeMs * 1_000_000)
+
+    fun asMapNs(): Map<BuildTime, Long> = buildTimesNs
+
+    fun asMapMs(): Map<BuildTime, Long> = buildTimesNs.mapValues { it.value / 1_000_000 }
 
     companion object {
         const val serialVersionUID = 0L

build-common/src/org/jetbrains/kotlin/build/report/metrics/DoNothingBuildMetricsReporter.kt

@@ -6,13 +6,13 @@
 package org.jetbrains.kotlin.build.report.metrics
 
 object DoNothingBuildMetricsReporter : BuildMetricsReporter {
-    override fun startMeasure(time: BuildTime, startNs: Long) {
+    override fun startMeasure(time: BuildTime) {
     }
 
-    override fun endMeasure(time: BuildTime, endNs: Long) {
+    override fun endMeasure(time: BuildTime) {
     }
 
-    override fun addTimeMetric(time: BuildTime, durationMs: Long) {
+    override fun addTimeMetricNs(time: BuildTime, durationNs: Long) {
     }
 
     override fun addMetric(metric: BuildPerformanceMetric, value: Long) {
@@ -28,5 +28,5 @@ object DoNothingBuildMetricsReporter : BuildMetricsReporter {
             BuildAttributes()
         )
 
-    override fun addMetrics(metrics: BuildMetrics?) {}
+    override fun addMetrics(metrics: BuildMetrics) {}
 }