SzyWilliam commented on code in PR #964:
URL: https://github.com/apache/ratis/pull/964#discussion_r1391934644
##########
ratis-server/src/main/java/org/apache/ratis/server/raftlog/segmented/SegmentedRaftLogOutputStream.java:
##########
@@ -98,19 +87,26 @@ public void write(LogEntryProto entry) throws IOException {
final int serialized = entry.getSerializedSize();
final int proto = CodedOutputStream.computeUInt32SizeNoTag(serialized) +
serialized;
final int total = proto + 4; // proto and 4-byte checksum
- final byte[] buf = sharedBuffer != null? sharedBuffer.get(): new
byte[total];
- Preconditions.assertTrue(total <= buf.length, () -> "total = " + total + "
> buf.length " + buf.length);
preallocateIfNecessary(total);
- CodedOutputStream cout = CodedOutputStream.newInstance(buf);
- cout.writeUInt32NoTag(serialized);
- entry.writeTo(cout);
+ out.writeToBuffer(total, buf -> {
+ final int pos = buf.position();
+ final int protoEndPos= pos + proto;
+
+ final CodedOutputStream encoder = CodedOutputStream.newInstance(buf);
+ encoder.writeUInt32NoTag(serialized);
+ entry.writeTo(encoder);
- checksum.reset();
- checksum.update(buf, 0, proto);
- ByteBuffer.wrap(buf, proto, 4).putInt((int) checksum.getValue());
+ // compute checksum
+ final ByteBuffer duplicated = buf.duplicate();
+ duplicated.position(pos).limit(protoEndPos);
+ checksum.reset();
+ checksum.update(duplicated);
Review Comment:
Since we are using `DirectByteBuffer` here, the checksum operation
essentially **reads all data from direct memory back to heap memory**. Even
worse, the `UsafeOperation` will do a lot of validations before each
`ByteBuffer.get`, leading to significant performance issues.
```java
// from DirectByteBuffer.java
public byte get(int i) {
try {
return ((SCOPED_MEMORY_ACCESS.getByte(session(), null,
ix(checkIndex(i)))));
} finally {
Reference.reachabilityFence(this);
}
}
```
Maybe we can found a way to compute checksum directly on `LogEntryProto`,
since it's a heap object?
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