8361076: Add benchmark for ImageReader in preparation for Valhalla changes

[david-beaumont]

Initial benchmark to capture at least some comparative measures of ImageReader performance.

Current results on my laptop:

Benchmark Mode Cnt Score Error Units
NewImageBenchmark.warmCache_CountAllNodes avgt 5 0.785 ± 0.140 ms/op
NewImageBenchmark.coldStart_CountOnly ss 5 34.051 ± 17.662 ms/op
NewImageBenchmark.coldStart_InitAndCount ss 5 31.006 ± 9.674 ms/op
NewImageBenchmark.coldStart_LoadJavacInitClasses ss 5 3.752 ± 6.873 ms/op

The upcoming changes to ImageReader should show significant improvements to these results.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issue

• JDK-8361076: Add benchmark for ImageReader in preparation for Valhalla changes (Bug - P4)

Reviewers

• Magnus Ihse Bursie (@magicus - Reviewer) 🔄 Re-review required (review applies to 089b68e2)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/26044/head:pull/26044
$ git checkout pull/26044

Update a local copy of the PR:
$ git checkout pull/26044
$ git pull https://git.openjdk.org/jdk.git pull/26044/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 26044

View PR using the GUI difftool:
$ git pr show -t 26044

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/26044.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back david-beaumont! 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]

@david-beaumont This change is no longer ready for integration - check the PR body for details.

[david-beaumont]

I removed a JrtFS related benchmark because it tracked the other one closely enough to not be worth it (hence only 1 additional module export needed).

[openjdk]

@david-beaumont The following labels will be automatically applied to this pull request:

• build
• core-libs

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 03: Full - Incremental (965abec0)
• 02: Full - Incremental (089b68e2)
• 01: Full - Incremental (489d720a)
• 00: Full (c9fbbffe)

[david-beaumont]

This comment might have been before I applied Scope.Benchmark to the states below. I'll double check if it's still an issue.

[david-beaumont]

Apologies. I realized the name for this class was still completely daft. After spending so much time looking at the details, I didn't spot the obvious.

[magicus]

Build change trivially fine.

/reviewers 2

[openjdk]

@magicus
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[AlanBateman]

I don't think this is maintainable. How useful (or not) is this benchmark if the names of all the internal classes (that will change from release to release) are dropped from this?

[david-beaumont]

Debatable. It's obviously going to scale any results somewhat based on the size of the resources and number of classes. It's kind nice to see "this change removes at least N micro/milli seconds of time spent" since that's a minimum set of classes we expect to always be needed, so any time saved is a lower bound.

I'd say maybe leave it as is for now with a note saying "if this keeps breaking, make the list less fragile".
I'm also assuming this is only run manually, and not a part of any CI pipeline ... so please let me know if I'm wrong about that.