diff --git a/jcstress-core/src/main/java/org/openjdk/jcstress/Options.java b/jcstress-core/src/main/java/org/openjdk/jcstress/Options.java
index f7b9ac08..f8e2ef68 100644
--- a/jcstress-core/src/main/java/org/openjdk/jcstress/Options.java
+++ b/jcstress-core/src/main/java/org/openjdk/jcstress/Options.java
@@ -51,15 +51,14 @@ public class Options {
private String resultDir;
private String testFilter;
private int minStride, maxStride;
- private int maxFootprint;
private int time;
private int iters;
private final String[] args;
private boolean parse;
private boolean list;
private Verbosity verbosity;
- private int totalCpuCount;
private int cpuCount;
+ private int heapPerFork;
private int forks;
private String mode;
private SpinLoopStyle spinStyle;
@@ -107,7 +106,7 @@ public boolean parse() throws IOException {
"Reducing the number of CPUs limits the amount of resources (including memory) the run is using.")
.withRequiredArg().ofType(Integer.class).describedAs("N");
- OptionSpec<Integer> maxFootprint = parser.accepts("mf", "Maximum footprint for each test, in megabytes. This " +
+ OptionSpec<Integer> heapPerFork = parser.accepts("hs", "Java heap size per fork, in megabytes. This " +
"affects the stride size: maximum footprint will never be exceeded, regardless of min/max stride sizes.")
.withRequiredArg().ofType(Integer.class).describedAs("MB");
@@ -181,7 +180,7 @@ public boolean parse() throws IOException {
this.verbosity = new Verbosity(0);
}
- totalCpuCount = VMSupport.figureOutHotCPUs();
+ int totalCpuCount = VMSupport.figureOutHotCPUs();
cpuCount = orDefault(set.valueOf(cpus), totalCpuCount);
if (cpuCount > totalCpuCount) {
@@ -236,7 +235,7 @@ public boolean parse() throws IOException {
this.minStride = orDefault(set.valueOf(minStride), 10);
this.maxStride = orDefault(set.valueOf(maxStride), 10000);
- this.maxFootprint = orDefault(set.valueOf(maxFootprint), 100);
+ this.heapPerFork = orDefault(set.valueOf(heapPerFork), 256);
this.jvmArgs = processArgs(optJvmArgs, set);
this.jvmArgsPrepend = processArgs(optJvmArgsPrepend, set);
@@ -345,10 +344,6 @@ public int getCPUCount() {
return cpuCount;
}
- public int getTotalCPUCount() {
- return totalCpuCount;
- }
-
public String getResultFile() {
return resultFile;
}
@@ -361,8 +356,13 @@ public Collection<String> getJvmArgsPrepend() {
return jvmArgsPrepend;
}
+ public int getHeapPerForkMb() {
+ return heapPerFork;
+ }
+
public int getMaxFootprintMb() {
- return maxFootprint;
+ // Half of heap size.
+ return getHeapPerForkMb() / 2;
}
}
diff --git a/jcstress-core/src/main/java/org/openjdk/jcstress/infra/grading/ReportUtils.java b/jcstress-core/src/main/java/org/openjdk/jcstress/infra/grading/ReportUtils.java
index 2a2f5c13..f835b049 100644
--- a/jcstress-core/src/main/java/org/openjdk/jcstress/infra/grading/ReportUtils.java
+++ b/jcstress-core/src/main/java/org/openjdk/jcstress/infra/grading/ReportUtils.java
@@ -209,11 +209,6 @@ private static boolean skipMessage(String data) {
return true;
}
- if (data.contains("Option MaxRAMFraction was deprecated in version") ||
- data.contains("Option MinRAMFraction was deprecated in version")) {
- return true;
- }
-
if (data.contains("compiler directives added")) {
return true;
}
diff --git a/jcstress-core/src/main/java/org/openjdk/jcstress/vm/VMSupport.java b/jcstress-core/src/main/java/org/openjdk/jcstress/vm/VMSupport.java
index 9bbe0b30..a18e0bfb 100644
--- a/jcstress-core/src/main/java/org/openjdk/jcstress/vm/VMSupport.java
+++ b/jcstress-core/src/main/java/org/openjdk/jcstress/vm/VMSupport.java
@@ -72,46 +72,51 @@ public static void initFlags(Options opts) {
"-XX:+UnlockDiagnosticVMOptions"
);
- // Rationale: every test VM uses at least 2 threads. Which means there are at max $CPU/2 VMs.
- // Reserving half of the RSS of each VM to Java heap leaves enough space for native RSS and
- // other processes. This means multiplying the factor by 2. These two adjustments cancel each
- // other.
- //
- // It does not matter if user requested lower number of VMs, we still want to follow
- // the global per-VM fraction. This would trim down the memory requirements along with
- // CPU requirements.
- //
- // Setting -Xms/-Xmx explicitly is supposed to override these defaults.
- //
- int part = opts.getTotalCPUCount();
-
- detect("Trimming down the default VM heap size to 1/" + part + "-th of max RAM",
+ // Tests are supposed to run in a very tight memory constraints:
+ // the test objects are small and reused where possible. The footprint
+ // testing machinery would select appropriate stride sizes to fit the heap.
+ // Users can override this to work on smaller/larger machines, but it should
+ // not be necessary, as even the smallest machines usually have more than 256M
+ // of system memory per CPU.
+
+ int heap = opts.getHeapPerForkMb();
+ detect("Trimming down the VM heap size to " + heap + "M",
SimpleTestMain.class,
GLOBAL_JVM_FLAGS,
- "-XX:MaxRAMFraction=" + part, "-XX:MinRAMFraction=" + part);
+ "-Xms" + heap + "M", "-Xmx" + heap + "M");
- detect("Trimming down the number of compiler threads",
- SimpleTestMain.class,
- GLOBAL_JVM_FLAGS,
- "-XX:CICompilerCount=2" // This is the absolute minimum for tiered configurations
- );
+ // The tests are usually not GC heavy. The minimum amount of threads a jcstress
+ // test uses is 2, so we can expect the CPU affinity machinery to allocate at
+ // least 2 CPUs per fork. This gives us the upper bound for the number of GC threads: 2,
+ // otherwise we risk oversubscribing the forked VM.
+ //
+ // We could, theoretically, drop the number of GC threads to 1, but GC ergonomics
+ // sometimes decides to switch to single-threaded mode in some GC implementations
+ // (e.g. for reference processing), and it would make sense to let GC run in multi-threaded
+ // modes instead.
detect("Trimming down the number of parallel GC threads",
SimpleTestMain.class,
GLOBAL_JVM_FLAGS,
- "-XX:ParallelGCThreads=4"
+ "-XX:ParallelGCThreads=2"
);
detect("Trimming down the number of concurrent GC threads",
SimpleTestMain.class,
GLOBAL_JVM_FLAGS,
- "-XX:ConcGCThreads=4"
+ "-XX:ConcGCThreads=2"
);
detect("Trimming down the number of G1 concurrent refinement GC threads",
SimpleTestMain.class,
GLOBAL_JVM_FLAGS,
- "-XX:G1ConcRefinementThreads=4"
+ "-XX:G1ConcRefinementThreads=2"
+ );
+
+ detect("Trimming down the number of compiler threads",
+ SimpleTestMain.class,
+ GLOBAL_JVM_FLAGS,
+ "-XX:CICompilerCount=2" // This is the absolute minimum for tiered configurations
);
detect("Testing @Contended works on all results and infra objects",