Hi,
I wonder why "isRecord" was not encoded in class modifier bits, like
"isEnum" was for example. Are all 32 bits already taken? The isEnum()
does not have the performance problem since getModifiers() native method
is intrinsified.
Regards, Peter
On 6/24/20 10:20 AM, Chris Hegarty wrote:
On 24 Jun 2020, at 07:03, David Holmes <david.hol...@oracle.com
<mailto:david.hol...@oracle.com>> wrote:
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
<mailto: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
Yeah, that seems reasonable. The extra bloat should be given due
consideration.
I’ve not yet counted how many of these isThis and isThat methods that
there are, but I suspect that there are enough that could warrant
their state being encoded into a single int or long value on j.l.Class
(that could be set lazily by the VM). This would setup a convenient
and reasonably efficient location to add future pieces of cached
state, like isSealed.
- 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.
It is relatively inexpensive to ask a non-record class if it is a
record, but the converse is not the case.
Java Serialization can probably “workaround” this, since it already
has a level of local-class cache state, so we can leverage that [*],
which is probably the right thing to do for Java Serialization anyway,
but I still think that there is a general tractable problem here.
-Chris.
[*]
diff -r 3a9521647349
src/java.base/share/classes/java/io/ObjectInputStream.java
--- a/src/java.base/share/classes/java/io/ObjectInputStream.javaTue
Jun 23 10:46:39 2020 +0100
+++ b/src/java.base/share/classes/java/io/ObjectInputStream.javaWed
Jun 24 09:07:07 2020 +0100
@@ -2182,7 +2182,7 @@
handles.markException(passHandle, resolveEx);
}
- final boolean isRecord = cl != null && isRecord(cl);
+ final boolean isRecord = desc.isRecord();
if (isRecord) {
assert obj == null;
obj = readRecord(desc);
