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Use MappedByteBuffer to load image.
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This simplifies the code, speeds up image loading, and reduces memory pressure at startup by mapping the image file into unmanaged memory.
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@fniephaus
fniephaus committed Oct 20, 2024
1 parent 9ad5043 commit 360bf42
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Showing 2 changed files with 79 additions and 101 deletions.
175 changes: 74 additions & 101 deletions src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageReader.java
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,12 @@
*/
package de.hpi.swa.trufflesqueak.image;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.nio.ByteOrder;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.HashSet;
import java.util.logging.Level;
Expand All @@ -31,7 +35,7 @@
import de.hpi.swa.trufflesqueak.util.ArrayUtils;
import de.hpi.swa.trufflesqueak.util.LogUtils;
import de.hpi.swa.trufflesqueak.util.MiscUtils;
import de.hpi.swa.trufflesqueak.util.VarHandleUtils;
import de.hpi.swa.trufflesqueak.util.UnsafeUtils;

public final class SqueakImageReader {
private static final byte[] EMPTY_BYTES = new byte[0];
Expand All @@ -40,14 +44,9 @@ public final class SqueakImageReader {

public final AddressToChunkMap chunkMap = new AddressToChunkMap();
public final SqueakImageContext image;
private final byte[] byteArrayBuffer = new byte[Long.BYTES];

private long oldBaseAddress;
private int headerSize;
private long specialObjectsPointer;
private long firstSegmentSize;
private int position;
private long currentAddressSwizzle;
private long dataSize;

private SqueakImageChunk freePageList;

Expand All @@ -72,9 +71,11 @@ private Object run() {
if (!truffleFile.isRegularFile()) {
throw SqueakException.create(MiscUtils.format("Image at '%s' does not exist.", image.getImagePath()));
}
try (BufferedInputStream inputStream = new BufferedInputStream(truffleFile.newInputStream())) {
readHeader(inputStream);
readBody(inputStream);
try (var channel = FileChannel.open(Path.of(image.getImagePath()), StandardOpenOption.READ)) {
final MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, channel.size());
buffer.order(ByteOrder.LITTLE_ENDIAN);
readImage(buffer);
UnsafeUtils.invokeCleaner(buffer);
} catch (final IOException e) {
throw SqueakException.create("Failed to read Smalltalk image:", e.getMessage());
}
Expand All @@ -84,128 +85,86 @@ private Object run() {
return image.getSqueakImage();
}

private static void readBytes(final BufferedInputStream stream, final byte[] bytes, final int length) throws IOException {
final int readBytes = stream.read(bytes, 0, length);
assert readBytes == length : "Failed to read bytes";
private static void skip(final MappedByteBuffer buffer, final int numBytes) {
buffer.position(buffer.position() + numBytes);
}

private long nextWord(final BufferedInputStream stream) throws IOException {
return nextLong(stream);
}

private short nextShort(final BufferedInputStream stream) throws IOException {
readBytes(stream, byteArrayBuffer, Short.BYTES);
position += Short.BYTES;
return VarHandleUtils.getShort(byteArrayBuffer, 0);
}

private int nextInt(final BufferedInputStream stream) throws IOException {
readBytes(stream, byteArrayBuffer, Integer.BYTES);
position += Integer.BYTES;
return VarHandleUtils.getInt(byteArrayBuffer, 0);
}

private long nextLong(final BufferedInputStream stream) throws IOException {
readBytes(stream, byteArrayBuffer, Long.BYTES);
position += Long.BYTES;
return VarHandleUtils.getLong(byteArrayBuffer, 0);
}

private byte[] nextObjectData(final BufferedInputStream stream, final int size, final int format) throws IOException {
if (size == 0) {
skipBytes(stream, SqueakImageConstants.WORD_SIZE); // skip trailing alignment word
return EMPTY_BYTES;
}
final int paddedObjectSize = size * SqueakImageConstants.WORD_SIZE;
final int padding = calculateObjectPadding(format);
final int objectDataSize = paddedObjectSize - padding;
final byte[] bytes = new byte[objectDataSize];
readBytes(stream, bytes, objectDataSize);
final long skipped = stream.skip(padding);
assert skipped == padding : "Failed to skip padding bytes";
position += paddedObjectSize;
return bytes;
}

private void skipBytes(final BufferedInputStream stream, final int count) throws IOException {
long pending = count;
while (pending > 0) {
final long skipped = stream.skip(pending);
assert skipped > 0 : "Nothing skipped, reached EOF?";
pending -= skipped;
}
position += count;
}

private void readHeader(final BufferedInputStream stream) throws IOException {
image.imageFormat = nextInt(stream);
private void readImage(final MappedByteBuffer buffer) {
// Read header
image.imageFormat = buffer.getInt();
if (!ArrayUtils.contains(SqueakImageConstants.SUPPORTED_IMAGE_FORMATS, image.imageFormat)) {
throw SqueakException.create(MiscUtils.format("Image format %s not supported. Please supply a compatible 64bit Spur image (%s).", image.imageFormat,
Arrays.toString(SqueakImageConstants.SUPPORTED_IMAGE_FORMATS)));
}

// Base header start
final int headerSize = nextInt(stream);
dataSize = nextWord(stream);
oldBaseAddress = nextWord(stream);
specialObjectsPointer = nextWord(stream);
nextWord(stream); // 1 word last used hash
final long snapshotScreenSize = nextWord(stream);
final long headerFlags = nextWord(stream);
nextInt(stream); // extraVMMemory
headerSize = buffer.getInt();
final long dataSize = buffer.getLong();
final long oldBaseAddress = buffer.getLong();
specialObjectsPointer = buffer.getLong();
// 1 word last used hash
buffer.getLong();
final long snapshotScreenSize = buffer.getLong();
final long headerFlags = buffer.getLong();
// extraVMMemory
buffer.getInt();

// Spur header start
nextShort(stream); // numStackPages
nextShort(stream); // cogCodeSize
assert position == 64 : "Wrong position";
nextInt(stream); // edenBytes
final short maxExternalSemaphoreTableSize = nextShort(stream);
nextShort(stream); // unused, realign to word boundary
assert position == 72 : "Wrong position";
firstSegmentSize = nextWord(stream);
nextWord(stream); // freeOldSpace
// numStackPages
buffer.getShort();
// cogCodeSize
buffer.getShort();
assert buffer.position() == 64 : "Wrong position";
// edenBytes
buffer.getInt();
final short maxExternalSemaphoreTableSize = buffer.getShort();
// unused, realign to word boundary
buffer.getShort();
assert buffer.position() == 72 : "Wrong position";
final long firstSegmentSize = buffer.getLong();
// freeOldSpace
buffer.getLong();

image.flags.initialize(oldBaseAddress, headerFlags, snapshotScreenSize, maxExternalSemaphoreTableSize);

skipBytes(stream, headerSize - position); // skip to body
}
skip(buffer, headerSize - buffer.position());
assert buffer.position() == headerSize;

private void readBody(final BufferedInputStream stream) throws IOException {
position = 0;
long segmentEnd = firstSegmentSize;
currentAddressSwizzle = oldBaseAddress;
while (position < segmentEnd) {
while (position < segmentEnd - SqueakImageConstants.IMAGE_BRIDGE_SIZE) {
final SqueakImageChunk chunk = readObject(stream);
// Read body
long segmentEnd = headerSize + firstSegmentSize;
long currentAddressSwizzle = oldBaseAddress;
while (buffer.position() < segmentEnd) {
while (buffer.position() < segmentEnd - SqueakImageConstants.IMAGE_BRIDGE_SIZE) {
final SqueakImageChunk chunk = readObject(buffer);
chunkMap.put(chunk.getPosition() + currentAddressSwizzle, chunk);
}
assert hiddenRootsChunk != null : "hiddenRootsChunk must be known from now on.";
final long bridge = nextLong(stream);
final long bridge = buffer.getLong();
long bridgeSpan = 0;
if ((bridge & SqueakImageConstants.SLOTS_MASK) != 0) {
bridgeSpan = bridge & ~SqueakImageConstants.SLOTS_MASK;
}
final long nextSegmentSize = nextLong(stream);
assert bridgeSpan >= 0 && nextSegmentSize >= 0 && position == segmentEnd;
final long nextSegmentSize = buffer.getLong();
assert bridgeSpan >= 0 && nextSegmentSize >= 0 && buffer.position() == segmentEnd;
if (nextSegmentSize == 0) {
break;
}
segmentEnd += nextSegmentSize;
currentAddressSwizzle += bridgeSpan * SqueakImageConstants.WORD_SIZE;
}
assert dataSize == position;
assert buffer.position() == headerSize + dataSize;
}

private SqueakImageChunk readObject(final BufferedInputStream stream) throws IOException {
int pos = position;
private SqueakImageChunk readObject(final MappedByteBuffer buffer) {
int pos = buffer.position() - headerSize;
assert pos % SqueakImageConstants.WORD_SIZE == 0 : "every object must be 64-bit aligned: " + pos % SqueakImageConstants.WORD_SIZE;
long headerWord = nextLong(stream);
long headerWord = buffer.getLong();
int numSlots = SqueakImageConstants.ObjectHeader.getNumSlots(headerWord);
if (numSlots == SqueakImageConstants.OVERFLOW_SLOTS) {
numSlots = (int) (headerWord & ~SqueakImageConstants.SLOTS_MASK);
assert numSlots >= SqueakImageConstants.OVERFLOW_SLOTS;
pos = position;
headerWord = nextLong(stream);
pos = buffer.position() - headerSize;
headerWord = buffer.getLong();
assert SqueakImageConstants.ObjectHeader.getNumSlots(headerWord) == SqueakImageConstants.OVERFLOW_SLOTS : "Objects with long header must have 255 in slot count";
}
final int size = numSlots;
Expand All @@ -215,10 +174,10 @@ private SqueakImageChunk readObject(final BufferedInputStream stream) throws IOE
if (ignoreObjectData(headerWord, classIndex, size)) {
/* Skip some hidden objects for performance reasons. */
objectData = null;
skipBytes(stream, size * SqueakImageConstants.WORD_SIZE);
skip(buffer, size * SqueakImageConstants.WORD_SIZE);
} else {
final int format = SqueakImageConstants.ObjectHeader.getFormat(headerWord);
objectData = nextObjectData(stream, size, format);
objectData = nextObjectData(buffer, size, format);
}
final SqueakImageChunk chunk = new SqueakImageChunk(this, headerWord, pos, objectData);
if (hiddenRootsChunk == null && isHiddenObject(classIndex)) {
Expand All @@ -234,6 +193,20 @@ private SqueakImageChunk readObject(final BufferedInputStream stream) throws IOE
return chunk;
}

private byte[] nextObjectData(final MappedByteBuffer buffer, final int size, final int format) {
if (size == 0) {
skip(buffer, SqueakImageConstants.WORD_SIZE); // skip trailing alignment word
return EMPTY_BYTES;
}
final int paddedObjectSize = size * SqueakImageConstants.WORD_SIZE;
final int padding = calculateObjectPadding(format);
final int objectDataSize = paddedObjectSize - padding;
final byte[] bytes = new byte[objectDataSize];
buffer.get(bytes);
skip(buffer, padding);
return bytes;
}

protected static boolean ignoreObjectData(final long headerWord, final int classIndex, final int size) {
return isFreeObject(classIndex) || isObjectStack(classIndex, size) || isHiddenObject(classIndex) && SqueakImageConstants.ObjectHeader.isPinned(headerWord);
}
Expand Down
5 changes: 5 additions & 0 deletions src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/util/UnsafeUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
package de.hpi.swa.trufflesqueak.util;

import java.lang.reflect.Field;
import java.nio.ByteBuffer;

import com.oracle.truffle.api.CompilerDirectives;

Expand Down Expand Up @@ -454,4 +455,8 @@ public static short[] toShorts(final long[] longs) {
UNSAFE.copyMemory(longs, Unsafe.ARRAY_LONG_BASE_OFFSET, shorts, Unsafe.ARRAY_SHORT_BASE_OFFSET, numBytes);
return shorts;
}

public static void invokeCleaner(final ByteBuffer directBuffer) {
UNSAFE.invokeCleaner(directBuffer);
}
}

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