CODETOOLS-7902866: JOL: Rework the instance dump output: formatting, decoding mark/class words, array length

[shipilev]

JOL already knows a lot about the target VM. It can also decode the object headers more verbosely.

JOLSample_14_FatLocking example output:

$ ~/Install/jdk11u-dev/bin/java -cp jol-samples/target/jol-samples.jar org.openjdk.jol.samples.JOLSample_14_FatLocking
# WARNING: Unable to get Instrumentation. Dynamic Attach failed. You may add this JAR as -javaagent manually, or supply -Djdk.attach.allowAttachSelf
# Running 64-bit HotSpot VM.
# Using compressed oop with 3-bit shift.
# Using compressed klass with 0x0000000800000000 base address and 0-bit shift.
# Objects are 8 bytes aligned.
# Field sizes by type: 4, 1, 1, 2, 2, 4, 4, 8, 8 [bytes]
# Array element sizes: 4, 1, 1, 2, 2, 4, 4, 8, 8 [bytes]

**** Fresh object
org.openjdk.jol.samples.JOLSample_14_FatLocking$A object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x0000000000000005 (biasable; age: 0)
  8   4        (object header: class)    0x000d5d08
 12   4        (object alignment gap)    
Instance size: 16 bytes
Space losses: 0 bytes internal + 4 bytes external = 4 bytes total

**** Before the lock
org.openjdk.jol.samples.JOLSample_14_FatLocking$A object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x00007f5eec70c005 (biased: 0x0000001fd7bb1c30; epoch: 0; age: 0)
  8   4        (object header: class)    0x000d5d08
 12   4        (object alignment gap)    
Instance size: 16 bytes
Space losses: 0 bytes internal + 4 bytes external = 4 bytes total

**** With the lock
org.openjdk.jol.samples.JOLSample_14_FatLocking$A object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x00007f5e64008682 (fat lock: 0x00007f5e64008682)
  8   4        (object header: class)    0x000d5d08
 12   4        (object alignment gap)    
Instance size: 16 bytes
Space losses: 0 bytes internal + 4 bytes external = 4 bytes total

**** After the lock
org.openjdk.jol.samples.JOLSample_14_FatLocking$A object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x00007f5e64008682 (fat lock: 0x00007f5e64008682)
  8   4        (object header: class)    0x000d5d08
 12   4        (object alignment gap)    
Instance size: 16 bytes
Space losses: 0 bytes internal + 4 bytes external = 4 bytes total

**** After System.gc()
org.openjdk.jol.samples.JOLSample_14_FatLocking$A object internals:
OFF  SZ   TYPE DESCRIPTION               VALUE
  0   8        (object header: mark)     0x0000000000000001 (non-biasable; age: 0)
  8   4        (object header: class)    0x000d5d08
 12   4        (object alignment gap)    
Instance size: 16 bytes
Space losses: 0 bytes internal + 4 bytes external = 4 bytes total

---

Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed

Issue

• CODETOOLS-7902866: JOL: Rework the instance dump output: formatting, decoding mark/class words, array length

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jol pull/11/head:pull/11
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$ git pull https://git.openjdk.java.net/jol pull/11/head

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$ git pr checkout 11

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https://git.openjdk.java.net/jol/pull/11.diff

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