[8u] RFR backport of JDK-8144732: VM_HeapDumper hits assert with bad dump_len

[Hohensee, Paul]

Thanks, Andrew. I've filed https://bugs.openjdk.java.net/browse/JDK-8235299 for the backport issue and https://bugs.openjdk.java.net/browse/JDK-8235299 for the associated CSR and assigned both to Denghui.

Paul

On 12/3/19, 2:57 PM, "Andrew Hughes" <gnu.andrew at redhat.com> wrote:

    
    
    On 06/11/2019 18:07, Hohensee, Paul wrote:
    > I found http://jperfanal.sourceforge.net/java.hprof.txt, which is a thread stack dump that references 1.0.1, is dated Dec 30, 2001, and the dump output is copyright 1998. So 1.0.1 is probably from 1998.
    > 
    > I found a file format spec at http://hg.openjdk.java.net/jdk6/jdk6/jdk/raw-file/tip/src/share/demo/jvmti/hprof/manual.html#mozTocId848088. It's from Java 6, so 1.0.2 was supported then. I also found
    > 
    > https://bugs.openjdk.java.net/browse/JDK-6305542: HPROF binary format needs to support large dumps
    > 
    > for Java 6, and
    > 
    > https://bugs.openjdk.java.net/browse/JDK-6313381: HPROF: agent should generate version 1.0.2 for large heaps
    > 
    > which updated the hprof agent to generate 1.0.2 format files for heaps > 4gb in Java 6, and
    > 
    > https://bugs.openjdk.java.net/browse/JDK-6313383: SA: Update jmap to support HPROF binary format "JAVA PROFILE 1.0.2"
    > 
    > which was shipped in 8u25 in 2014.
    > 
    > So, JDKs/JREs starting with Java 6 can read 1.0.2 files, and the SA can read them starting with 8u25. I don't think we need to worry about using Java 5 to read files generated by Java 8, and the SA is good to go for 8.
    > 
    > Paul
    > 
    
    Thanks for the through research. My concern is not so much whether the
    format can be read, as whether it is expected on small heap dumps.
    JDK-6313383 also says "For compatibility it would be best if jmap
    continued to generate a 1.0.1 format for smaller heaps (<2GB for example).".
    
    I think this may warrant a CSR.
    
    Thanks,
    -- 
    Andrew :)
    
    Senior Free Java Software Engineer
    Red Hat, Inc. (http://www.redhat.com)
    
    PGP Key: ed25519/0xCFDA0F9B35964222 (hkp://keys.gnupg.net)
    Fingerprint = 5132 579D D154 0ED2 3E04  C5A0 CFDA 0F9B 3596 4222