8382295: Shenandoah: wrong denominator in full gc summary

[rgithubli]

When printing full gc summary, it prints out the percentage of explicit (System,gc()) and implicit GCs.

In the full GC section, its dominator is currently set to be concurrent GC count, which is wrong. The denominator should be the full gc count.

GHA passed.

Local testing: Run a simple app with two System.gc() calls. Before the change:

[6.077s][info][gc,stats       ]    15 Completed GCs
[6.077s][info][gc,stats       ]       2 caused by System.gc() (13.33%)
[6.077s][info][gc,stats       ]      13 caused by Concurrent GC (86.67%)
[6.077s][info][gc,stats       ] 
[6.077s][info][gc,stats       ]    13 Successful Concurrent GCs (86.67%)
[6.077s][info][gc,stats       ]      11 abbreviated (84.62%)
[6.077s][info][gc,stats       ] 
[6.077s][info][gc,stats       ]     0 Degenerated GCs (0.00%)
[6.077s][info][gc,stats       ]       0 upgraded to Full GC (0.00%)
[6.077s][info][gc,stats       ]       0 caused by allocation failure (0.00%)
[6.077s][info][gc,stats       ]       0 abbreviated (0.00%)
[6.077s][info][gc,stats       ] 
[6.077s][info][gc,stats       ]     2 Full GCs (13.33%)
[6.077s][info][gc,stats       ]       2 invoked explicitly (15.38%)
[6.077s][info][gc,stats       ]       0 invoked implicitly (0.00%)
[6.077s][info][gc,stats       ]       0 caused by allocation failure (0.00%)
[6.077s][info][gc,stats       ]       0 upgraded from Degenerated GC (0.00%)
[6.077s][info][gc,stats       ] 

After change:

[6.809s][info][gc,stats       ]    16 Completed GCs
[6.809s][info][gc,stats       ]       2 caused by System.gc() (12.50%)
[6.809s][info][gc,stats       ]      14 caused by Concurrent GC (87.50%)
[6.809s][info][gc,stats       ] 
[6.809s][info][gc,stats       ]    14 Successful Concurrent GCs (87.50%)
[6.809s][info][gc,stats       ]      12 abbreviated (85.71%)
[6.809s][info][gc,stats       ] 
[6.809s][info][gc,stats       ]     0 Degenerated GCs (0.00%)
[6.809s][info][gc,stats       ]       0 upgraded to Full GC (0.00%)
[6.809s][info][gc,stats       ]       0 caused by allocation failure (0.00%)
[6.809s][info][gc,stats       ]       0 abbreviated (0.00%)
[6.809s][info][gc,stats       ] 
[6.809s][info][gc,stats       ]     2 Full GCs (12.50%)
[6.809s][info][gc,stats       ]       2 invoked explicitly (100.00%)
[6.809s][info][gc,stats       ]       0 invoked implicitly (0.00%)
[6.809s][info][gc,stats       ]       0 caused by allocation failure (0.00%)
[6.809s][info][gc,stats       ]       0 upgraded from Degenerated GC (0.00%)
[6.809s][info][gc,stats       ] 

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Issue

• JDK-8382295: Shenandoah: wrong denominator in full gc summary (Bug - P4)

Reviewers

• Aleksey Shipilev (@shipilev - Reviewer)
• Kelvin Nilsen (@kdnilsen - Reviewer)

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8382295: Shenandoah: wrong denominator in full gc summary

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At the time when this comment was updated there had been 18 new commits pushed to the master branch:

• 10e23dd: 8382257: Shenandoah: Clean up stack watermark barrier support
• 17ee366: 8382150: Shenandoah: Clean up nmethod entry barrier support
• 2c30f12: 8347248: Rename arg_count to arg_size
• ... and 15 more: https://git.openjdk.org/jdk/compare/a2e840fd7413cbcbd663a30cb5681557e6142319...master

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[mlbridge]

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• 00: Full (7d9191da)

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[shipilev]

Looks correct.

[kdnilsen]

One question: do we have to worry about _success_full_gcs equal zero causing a divide by zero?

[rgithubli]

One question: do we have to worry about _success_full_gcs equal zero causing a divide by zero?

It's handled by percent_of: return denominator != 0 ? (double)numerator / (double)denominator * 100.0 : 0.0;

[rgithubli]

/integrate

[openjdk]

@rgithubli
Your change (at version 7d9191d) is now ready to be sponsored by a Committer.

[shipilev]

/sponsor

[openjdk]

Going to push as commit 2999731.
Since your change was applied there have been 21 commits pushed to the master branch:

• cbb85a5: 8382211: Shenandoah: Clean up and wire up final verification
• 93aa646: 8367761: [VectorAPI] AssertionError with several vector API mathlib tests with MaxVectorSize=32
• 1150750: 8382199: Remove unused parameter "dst" from CardTableBarrierSetAssembler::store_check()
• ... and 18 more: https://git.openjdk.org/jdk/compare/a2e840fd7413cbcbd663a30cb5681557e6142319...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev @rgithubli Pushed as commit 2999731.

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