Hi Chris,
On 24/06/2020 2:30 am, Chris Hegarty wrote:
On 23 Jun 2020, at 14:49, Peter Levart <peter.lev...@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 [*].
There has been reluctance to add more and more fields to Class to cache
all these new attributes that are being added - but ultimately that is a
call for core-libs folk to make. The general expectation is/was that the
need to ask a class if it is a Record (or isSealed etc) would be rare.
But (de)serialization is the exception for isRecord() as unlike enums a
simple instanceof test can't be used.
Cheers,
David
-----
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) {
