[Dist] enable USE_EPOLL in default

[Rhett-Ying]

Description

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature]])
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented
• To the best of my knowledge, examples are either not affected by this change,
  or have been fixed to be compatible with this change
• Related issue is referred in this PR
• If the PR is for a new model/paper, I've updated the example index here.

Changes

[dgl-bot]

To trigger regression tests:

• @dgl-bot run [instance-type] [which tests] [compare-with-branch];
  For example: @dgl-bot run g4dn.4xlarge all dmlc/master or @dgl-bot run c5.9xlarge kernel,api dmlc/master

[dgl-bot]

Commit ID: f2dfa3dc15d2376149bb6618f6ba74b50d2c9284

Build ID: 1

Status: ❌ CI test failed in Stage [Lint Check].

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Commit ID: 79cec6f

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Commit ID: c923832

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Commit ID: ec1bd1f

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Commit ID: 0aa5c25

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Commit ID: fc2072f

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Commit ID: 388a468

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Commit ID: 1f077d5

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Status: ✅ CI test succeeded

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[zheng-da]

what is this?

[Rhett-Ying]

if INCLUDE(CheckIncludeFile) is not added, error is Unknown CMake command 'check_include_file'.

[engaineer]

@Rhett-Ying Changing to use epoll by default breaks macOS build on either x86_64 or arm64 arch.

dgl/CMakeLists.txt

Line 38 in 9d42531

dgl_option(USE_EPOLL "Build with epoll for socket communicator" ON)

Temporary measure suggetions:

• Update build docs to add compiler flag -DUSE_EPOLL=OFF
• Update CMakeLists.txt to detect STREQUAL "Darwin" and revert to setting to USE_EPOLL=OFF and print a warning.

It's a great idea to use epoll to manage the socketpool but not cross-platform friendly. Is PR open to replace with something else like libuv, or is there another plan?

[Rhett-Ying]

Thanks for reporting this. I will fix it.

[Rhett-Ying]

@engaineer pls try with the latest master branch...

[engaineer]

@engaineer pls try with the latest master branch...

Clean build on macOS 12.4 arch arm64 for master with HEAD 1518861.

Thanks for being awesome and providing a prompt fix and refinement.