package eu.javaspecialists.tjsn.issue306;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.function.Predicate;
import java.util.stream.Stream;
import org.netbeans.lib.profiler.heap.HeapFactory;
import org.netbeans.lib.profiler.heap.Instance;
import org.netbeans.lib.profiler.heap.PrimitiveArrayInstance;
import static java.nio.charset.StandardCharsets.ISO_8859_1;
import static java.nio.charset.StandardCharsets.UTF_16LE;
public class HeapAnalysis {
private enum Coder {LATIN1, UTF16}
private record StringData(Coder coder, int length) {}
public static void main(String... args) throws IOException {
if (args.length < 1 || args.length > 2 ||
args.length > 1 && !args[0].equals("-verbose")) {
System.err.println("Usage: java HeapAnalysis " +
"[-verbose] heapdump");
System.exit(1);
}
var verbose = args.length == 2;
var filename = args[args.length - 1];
System.out.println("Inspecting heap file " + filename);
var heap = HeapFactory.createHeap(new File(filename));
var stringClass = heap.getJavaClassByName(
"java.lang.String");
var instances = stringClass.getInstancesIterator();
var stats = extractStringData(instances, verbose);
printStatistics(stats);
}
private static List<StringData> extractStringData(
Iterator<Instance> instances, boolean verbose) {
var result = new ArrayList<StringData>();
while (instances.hasNext()) {
Instance instance = instances.next();
Coder coder = getCoder(instance);
int length = getLength(instance, coder, verbose);
result.add(new StringData(coder, length));
}
return result;
}
private static Coder getCoder(Instance instance) {
Byte coder = (Byte) instance.getValueOfField("coder");
return switch (coder) {
case 0 -> Coder.LATIN1;
case 1 -> Coder.UTF16;
case null -> throw new IllegalStateException(
"Analysis for Java 11+ heap dumps only -"
+ " field coder not found in"
+ " java.lang.String");
default -> throw new IllegalStateException(
"Unknown coder: " + coder);
};
}
private static int getLength(Instance instance, Coder coder,
boolean verbose) {
var array = (PrimitiveArrayInstance)
instance.getValueOfField("value");
if (array == null)
throw new IllegalStateException(
"java.lang.String instances did not have a"
+ " value array field");
int length = array.getLength();
if (verbose) {
List<String> arrayValues = array.getValues();
byte[] bytes = new byte[length];
int i = 0;
for (String str : arrayValues)
bytes[i++] = Byte.parseByte(str);
System.out.println(switch (coder) {
case LATIN1 -> "LATIN1: "
+ new String(bytes, ISO_8859_1);
case UTF16 -> "UTF16: "
+ new String(bytes, UTF_16LE);
});
}
return length;
}
private static final Predicate<StringData> LATIN1_FILTER =
datum -> datum.coder() == Coder.LATIN1;
private static final Predicate<StringData> UTF16_FILTER =
datum -> datum.coder() == Coder.UTF16;
private static void printStatistics(List<StringData> data) {
long j8Memory = memoryUsed(data.stream(), 2);
long j11MemoryLatin1 =
memoryUsed(data.stream().filter(LATIN1_FILTER), 1);
long j11MemoryUTF16 =
memoryUsed(data.stream().filter(UTF16_FILTER), 2);
long j11Memory = j11MemoryLatin1 + j11MemoryUTF16;
var latin1Size = data.stream().filter(LATIN1_FILTER).count();
var utf16Size = data.stream().filter(UTF16_FILTER).count();
System.out.printf(Locale.US, """
Total number of String instances:
LATIN1 %,d
UTF16 %,d
Total %,d
""",
latin1Size, utf16Size, latin1Size + utf16Size);
System.out.printf(Locale.US, """
Java 8 memory used by String instances:
Total %,d bytes
""", j8Memory);
System.out.printf(Locale.US, """
Java 11+ memory used by String instances:
LATIN1 %,d bytes
UTF16 %,d bytes
Total %,d bytes
""", j11MemoryLatin1, j11MemoryUTF16, j11Memory);
System.out.printf(Locale.US, "Saving of %.2f%%%n", 100.0 *
(j8Memory - j11Memory) / j8Memory);
}
private static int memoryUsed(Stream<StringData> stats,
int bytesPerChar) {
return stats
.mapToInt(datum -> getStringSize(datum.length(),
bytesPerChar))
.sum();
}
private static int getStringSize(int length, int bytesPerChar) {
return 24 + 16 +
(int) (Math.ceil(length * bytesPerChar / 8.0) * 8);
}
}
|