Request for Review: JDK-8008796: SA: Oop.iterateFields() should support CompressedKlassPointers again
Krystal Mo
krystal.mo at oracle.com
Fri Mar 15 10:55:39 PDT 2013
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 <krystal.mo at oracle.com>
Organization: Oracle Corporation
To: "云达(Yunda)" <yunda.mly at taobao.com>
CC: serviceability-dev at openjdk.java.net
<serviceability-dev at openjdk.java.net>
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: yunda.mly at taobao.com
Thanks,
Kris
On 2013/2/25 17:14, 云达(Yunda) wrote:
>
> Kris,
>
> Thanks a lot!
>
> Regards,
>
> Yunda
>
> *From:*serviceability-dev-bounces at openjdk.java.net
> [mailto:serviceability-dev-bounces at openjdk.java.net] *On Behalf Of
> *Krystal Mo
> *Sent:* Monday, February 25, 2013 7:19 PM
> *To:* serviceability-dev at openjdk.java.net
> *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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