8257149: Improve G1 Service thread task scheduling to guarantee task delay

[albertnetymk]

Adopt the "at-least" semantics for scheduling delays in G1 service thread scheduling API so that a task is never scheduled earlier than it asked for. IOW, schedule_task(task, delay_ms) means task will run after >= delay_ms has passed.

Inspecting the logs (-Xlog:gc,gc+task*=trace) and focusing lines containing (Remembered Set Sampling Task) (schedule), we can see at what time the sampling task is scheduled.

Without ceil, sampling task could be scheduled more frequent than intended:

[0.321s][trace][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (schedule) @0.322s
[0.321s][debug][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (run) 0.042ms (cpu: 0.000ms)
[0.321s][debug][gc,task,start] G1 Service Thread (Remembered Set Sampling Task) (run)
[0.321s][trace][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (schedule) @0.322s
[0.321s][debug][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (run) 0.010ms (cpu: 0.000ms)
[0.321s][debug][gc,task,start] G1 Service Thread (Remembered Set Sampling Task) (run)
[0.321s][trace][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (schedule) @0.322s
[0.321s][debug][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (run) 0.008ms (cpu: 0.000ms)
[0.321s][debug][gc,task,start] G1 Service Thread (Remembered Set Sampling Task) (run)

With ceil; there's 300ms (G1ConcRefinementServiceIntervalMillis) interval btw each scheduling of the sampling task.

[0.093s][trace][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (schedule) @0.323s
[0.093s][debug][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (run) 0.006ms (cpu: 0.000ms)
[0.093s][debug][gc,task,start] G1 Service Thread (Periodic GC Task) (run)
[0.093s][trace][gc,task      ] G1 Service Thread (Periodic GC Task) (schedule) @1.093s
[0.093s][debug][gc,task      ] G1 Service Thread (Periodic GC Task) (run) 0.004ms (cpu: 0.000ms)
[0.093s][trace][gc,task      ] G1 Service Thread (wait) 0.230s
[0.323s][debug][gc,task,start] G1 Service Thread (Remembered Set Sampling Task) (run)
[0.323s][trace][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (schedule) @0.623s
[0.323s][debug][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (run) 0.024ms (cpu: 0.000ms)
[0.323s][trace][gc,task      ] G1 Service Thread (wait) 0.300s
[0.623s][debug][gc,task,start] G1 Service Thread (Remembered Set Sampling Task) (run)
[0.623s][trace][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (schedule) @0.923s
[0.623s][debug][gc,task      ] G1 Service Thread (Remembered Set Sampling Task) (run) 0.026ms (cpu: 0.000ms)
[0.623s][trace][gc,task      ] G1 Service Thread (wait) 0.300s

Tested: tier1 and manually checking the logs.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Testing

	Linux x64	Linux x86	Windows x64	macOS x64
Build	❌ (1/2 failed)	✔️ (2/2 passed)	❌ (1/2 failed)	✔️ (2/2 passed)
Test (tier1)		⏳ (3/9 running)		⏳ (1/9 running)

Failed test tasks

• Linux x64 (build debug)
• Windows x64 (build debug)

Issue

• JDK-8257149: Improve G1 Service thread task scheduling to guarantee task delay

Reviewers

• Stefan Johansson (@kstefanj - Reviewer) ⚠️ Review applies to ff513b0
• Ivan Walulya (@walulyai - Committer) ⚠️ Review applies to ff513b0

Download

$ git fetch https://git.openjdk.java.net/jdk pull/1451/head:pull/1451
$ git checkout pull/1451

[bridgekeeper]

👋 Welcome back ayang! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@albertnetymk The following label will be automatically applied to this pull request:

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[mlbridge]

Webrevs

• 02: Full (8de51d2)
• 01: Full - Incremental (92f8fbd)
• 00: Full (ff513b0)

[kstefanj]

Thanks for fixing this Albert, just a few small comments. If you don't agree just leave them as is.

[openjdk]

@albertnetymk This change now passes all automated pre-integration checks.

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8257149: Improve G1 Service thread task scheduling to guarantee task delay

Reviewed-by: sjohanss, iwalulya

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[albertnetymk]

All suggestions are applied; thanks for the review.

[albertnetymk]

/integrate

[openjdk]

@albertnetymk
Your change (at version 8de51d2) is now ready to be sponsored by a Committer.

[kstefanj]

/sponsor

[openjdk]

@kstefanj @albertnetymk Pushed as commit 20525d2.

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