8295798: (ch) Test java/nio/channels/Channels/ReadXBytes.java is very slow on Windows

[djelinski]

Please review this PR that reduces the number of bytes written by ReadXBytes test on machines supporting sparse files.

Before this change the createFileWithRandomContent function would usually write either the last byte only, or the entire file (long p was usually set to length - 1). Now the function only writes the first and the last 32kB, and the remaining bytes are initialized in platform-defined manner.

Before this change the test took between 1-10 minutes to complete on our Windows CI machines.
After this change the test finishes in less than 1 minute.

---

Progress

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

Issue

• JDK-8295798: (ch) Test java/nio/channels/Channels/ReadXBytes.java is very slow on Windows

Reviewers

• Alan Bateman (@AlanBateman - Reviewer) ⚠️ Review applies to 70f4b4bf
• Brian Burkhalter (@bplb - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/10834/head:pull/10834
$ git checkout pull/10834

Update a local copy of the PR:
$ git checkout pull/10834
$ git pull https://git.openjdk.org/jdk pull/10834/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 10834

View PR using the GUI difftool:
$ git pr show -t 10834

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/10834.diff

[bridgekeeper]

👋 Welcome back djelinski! 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]

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

• nio

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[mlbridge]

Webrevs

• 01: Full - Incremental (f5229267)
• 00: Full (70f4b4bf)

[AlanBateman]

This looks good, I assume you'll update the end date in the header before you integrate.

[openjdk]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8295798: (ch) Test java/nio/channels/Channels/ReadXBytes.java is very slow on Windows

Reviewed-by: alanb, bpb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 10 new commits pushed to the master branch:

• fefbddf: 8291443: Obsolete the PrintSharedDictionary flag
• 5b3de6e: 8284840: Update CLDR to Version 42.0
• 2f3f3b6: 8295792: Clean up old async close code
• 5ac6f18: 8290010: IGV: Fix UndoRedo Action
• c055dfc: 8294565: IGV: ClassCastException when clicking on an edge in the graph
• 3898385: 8295461: IGV: Wrong src/dest nodes highlighted for edge
• d50b6eb: 8295776: [JVMCI] Add x86 CPU flags for MPK and CET
• 5596d9a: 8288493: Document JDK specific system properties in jdk.httpserver
• 7a49c9b: 8295717: Minimize disabled warnings in accessibility native code
• 7460661: 8294466: Minimize disabled warnings in java.desktop

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[bplb]

Looks good, thanks.

[djelinski]

Thanks for the reviews!

/integrate

[openjdk]

Going to push as commit 706d1b7.
Since your change was applied there have been 17 commits pushed to the master branch:

• 89dafc0: 8292699: Improve printing of classes in native debugger
• 7520d0a: 8295855: ProblemList jdk/jshell/CommandCompletionTest.java on linux-all
• 1d15e5c: 8295716: Minimize disabled warnings in security libs
• 8c86e92: 8295847: slow debug build error after JDK-8294466
• e122321: 8295844: jdk/test/whitebox/CPUInfoTest.java failed with "not all features are known: expected true, was false"
• df81b3c: 8295738: Automate javax/swing/JFileChooser/FileSizeCheck.java
• 68cf248: 8295298: Automate javax/swing/JFileChooser/FileViewNPETest.java
• fefbddf: 8291443: Obsolete the PrintSharedDictionary flag
• 5b3de6e: 8284840: Update CLDR to Version 42.0
• 2f3f3b6: 8295792: Clean up old async close code
• ... and 7 more: https://git.openjdk.org/jdk/compare/89a94d050263fb5f71fabb32daa7949e137313e4...master

Your commit was automatically rebased without conflicts.

[openjdk]

@djelinski Pushed as commit 706d1b7.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.