cc'ing hotspot-runtime for a review
-------- Original Message --------
Subject: Request for Review: JDK-8008796: SA: Oop.iterateFields()
should support CompressedKlassPointers again
Date: Mon, 25 Feb 2013 18:03:20 -0800
From: Krystal Mo <[email protected]>
Organization: Oracle Corporation
To: "云达(Yunda)" <[email protected]>
CC: [email protected]
<[email protected]>
Hi all,
Could I have a review for this small change, please?
Webrev: http://cr.openjdk.java.net/~kmo/8008796/webrev.00/
CR: http://bugs.sun.com/view_bug.do?bug_id=8008796 (should be available
externally soon)
8008796: SA: Oop.iterateFields() should support CompressedKlassPointers
again
Summary: add a missing change from JDK-7054512 so that
Oop.iterateFields() works with UseCompressedKlassPointers
Reviewed-by: ?
Contributed-by: [email protected]
Thanks,
Kris
On 2013/2/25 17:14, 云达(Yunda) wrote:
Kris,
Thanks a lot!
Regards,
Yunda
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of
*Krystal Mo
*Sent:* Monday, February 25, 2013 7:19 PM
*To:* [email protected]
*Subject:* Re: Oop.iterateFields() should support
CompressedKlassPointers again
Hi Yunda,
Thanks for fixing this. I actually have the exact same fix for this
problem, along with fixes for some other problems in SA in my local
workspace, but haven't come around to sending it out for public review
yet.
I think this is just a missed change in JDK-7054512. I have created a
JIRA issue for you: JDK-8008796: SA: Oop.iterateFields() should
support CompressedKlassPointers again. I'll prepare a webrev and send
it out for official review later.
Thanks,
Kris
On 2013/2/25 2:58, 云达(Yunda) wrote:
Hi all,
When I used CLHSDB just now I met this error:
hsdb> inspect 0x00000000ee255080
instance of "java/io/InputStream" @ 0x00000000ee255080 @
0x00000000ee255080 (size = 24)
Exception in thread "main" java.lang.InternalError: unimplemented
at sun.jvm.hotspot.oops.Oop.iterateFields(Oop.java:151)
at
sun.jvm.hotspot.oops.Instance.iterateFields(Instance.java:66)
at sun.jvm.hotspot.oops.Oop.iterate(Oop.java:143)
at
sun.jvm.hotspot.ui.tree.OopTreeNodeAdapter.getChildCount(OopTreeNodeAdapter.java:65)
at
sun.jvm.hotspot.CommandProcessor$Command.printNode(CommandProcessor.java:231)
at
sun.jvm.hotspot.CommandProcessor$24.doit(CommandProcessor.java:1008)
at
sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:1897)
at
sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:1867)
at
sun.jvm.hotspot.CommandProcessor.run(CommandProcessor.java:1747)
at sun.jvm.hotspot.CLHSDB.run(CLHSDB.java:91)
at sun.jvm.hotspot.CLHSDB.main(CLHSDB.java:35)
I found it’s caused by the code of
sun.jvm.hotspot.oops.Oop.iterateFields():
void iterateFields(OopVisitor visitor, boolean doVMFields) {
if (doVMFields) {
visitor.doCInt(mark, true);
if (VM.getVM().isCompressedKlassPointersEnabled()) {
*throw new InternalError("unimplemented");*
} else {
visitor.doMetadata(klass, true);
}
}
}
When compressed oops( which is by default) are used an
InternalError of “unimplemented” will be throwed. But actually it
can be implemented easily by just one line of code:
visitor.doMetadata(compressedKlass, true);
I checked the hotspot-rt repo and I found it was implemented this
way before changeset 3601, the main implementation of NPG. Since
3601 changed a whole lot of stuff, the ‘compressedKlass’ field
couldn’t get the right value, as in line 51:
// compressedKlass = new
CIntField(type.getCIntegerField("_metadata._compressed_klass"), 0);
So the code in iterateFields() was changed to throwing an
InternalError accordingly.
But the ‘compressedKlass’ field can get the right value now. So I
think it’s time to change the code back and here’s the diff
against the latest hotspot-rt:
diff -r 2f881161d085
agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java
--- a/agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java Mon
Feb 25 18:25:24 2013 +0800
+++ b/agent/src/share/classes/sun/jvm/hotspot/oops/Oop.java Mon
Feb 25 18:47:08 2013 +0800
@@ -148,7 +148,7 @@
if (doVMFields) {
visitor.doCInt(mark, true);
if (VM.getVM().isCompressedKlassPointersEnabled()) {
- throw new InternalError("unimplemented");
+ visitor.doMetadata(compressedKlass, true);
} else {
visitor.doMetadata(klass, true);
}
Regards,
Yunda
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