RFR: 8247532, 8248135: Records deserialization is slow + Build microbenchmarks with --enable-preview

[Chris Hegarty]

> On 23 Jun 2020, at 14:49, Peter Levart <peter.levart at gmail.com> wrote:
> 
> ...
> 
> Ok, I'm going to push this to jdk15.

Thank you Peter. This is a really nice change.

As a follow on, and not for JDK 15, I observe that Class::isRecord0 / JVM_IsRecord shows up as consuming a significant amount of time, more than 10%, in some runs of the deserialization benchmark. The isRecord implementation is a native method in the JVM, so relatively expensive to call.

This shows an opportunity to improve the Class::isRecord implementation with a simple cache of the record-ness of the j.l.Class, as is done selectively with other particular aspects of a class’s state. There are various ways to implement this, but here is just one [*].

Running the deserialization benchmark with this change [*], gives the following results:

Benchmark                                    (length)  Mode  Cnt    Score    Error  Units
RecordSerializationBench.deserializeClasses        10  avgt   10   14.136 ±  0.841  us/op
RecordSerializationBench.deserializeClasses       100  avgt   10   61.821 ±  1.279  us/op
RecordSerializationBench.deserializeClasses      1000  avgt   10  519.473 ±  7.950  us/op
RecordSerializationBench.deserializeRecords        10  avgt   10   13.781 ±  1.917  us/op
RecordSerializationBench.deserializeRecords       100  avgt   10   54.061 ±  4.188  us/op
RecordSerializationBench.deserializeRecords      1000  avgt   10  444.538 ± 13.940  us/op

I think it is worth considering caching the record-ness state of a j.l.Class, as I’m sure it will be widely used in third-party serialization libraries, as well as by Java Serialization.

-Chris.

[*]
diff -r 3a9521647349 src/java.base/share/classes/java/lang/Class.java
--- a/src/java.base/share/classes/java/lang/Class.java	Tue Jun 23 10:46:39 2020 +0100
+++ b/src/java.base/share/classes/java/lang/Class.java	Tue Jun 23 17:11:35 2020 +0100
@@ -3712,9 +3712,17 @@
     @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.RECORDS,
                                  essentialAPI=false)
     public boolean isRecord() {
-        return getSuperclass() == JAVA_LANG_RECORD_CLASS && isRecord0();
+        if (!isRecordCalled) {
+            isRecord = getSuperclass() == JAVA_LANG_RECORD_CLASS && isRecord0();
+            isRecordCalled = true;
+        }
+        return isRecord;
     }
 
+    // cached record(ness) status
+    private transient boolean isRecord;
+    private transient boolean isRecordCalled;
+
     // Fetches the factory for reflective objects
     private static ReflectionFactory getReflectionFactory() {
         if (reflectionFactory == null) {