Use less threads than we have cores on Jenkins, increase max heap

Using less threads should allow us to increase the maximum heap size
without filling up the memory of the Jenkins instance

Author: smarter

project/Build.scala

@@ -6,9 +6,7 @@ import scala.reflect.io.Path
 
 object DottyBuild extends Build {
 
-  // Currently, this cannot be increased without hitting the maximum amount of memory
-  // available on the Jenkins VMs
-  val travisMemLimit = List("-Xmx1100m")
+  val travisMemLimit = List("-Xmx1500m")
 
   val JENKINS_BUILD = "dotty.jenkins.build"
 

test/dotty/partest/DPConsoleRunner.scala

@@ -68,8 +68,15 @@ class DPSuiteRunner(testSourcePath: String, // relative path, like "files", or "
   scalacExtraArgs: Seq[String] = Seq.empty)
 extends SuiteRunner(testSourcePath, fileManager, updateCheck, failed, javaCmdPath, javacCmdPath, scalacExtraArgs) {
 
+  val isJenkins = sys.props.isDefinedAt("dotty.jenkins.build")
+  val numCores = Runtime.getRuntime.availableProcessors
+
   if (!DPConfig.runTestsInParallel)
     sys.props("partest.threads") = "1"
+  else if (isJenkins)
+    sys.props("partest.threads") = (numCores / 2).toString
+  else
+    sys.props("partest.threads") = numCores.toString
 
   sys.props("partest.root") = "."