[GraphBolt] Always enable prefetch before CopyTo.

[mfbalin]

Description

The only difference between the new dataloader CopyTo related code and old code replaced in #7603 is the change in this PR. I am hoping it will fix the regression we are having in the cpu-cpu case.

I don't know why disabling prefetch in the CPU only case would cause a regression.

@frozenbugs can we test if this PR fixes the regression issue for the cpu-cpu case? I can't seem to reliably verify it but I strongly suspect this PR will fix it.

Checklist

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [$CATEGORY] (such as [NN], [Model], [Doc], [Feature]])
• I've leverage the tools to beautify the python and c++ code.
• The PR is complete and small, read the Google eng practice (CL equals to PR) to understand more about small PR. In DGL, we consider PRs with less than 200 lines of core code change are small (example, test and documentation could be exempted).
• 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: a7ccc7f

Build ID: 1

Status: ✅ CI test succeeded.

Report path: link

Full logs path: link

[frozenbugs]

Yes, this PR fixes the issue.

'graphbolt' 'exclude_edges' 'cpu-cpu' 133.32784
'graphbolt' 'not_exclude_edges' 'cpu-cpu' 135.22002

[frozenbugs]

Please clean up the code and merge it.

[mfbalin]

Yes, this PR fixes the issue.

'graphbolt' 'exclude_edges' 'cpu-cpu' 133.32784 'graphbolt' 'not_exclude_edges' 'cpu-cpu' 135.22002

Thanks for verifying. For some reason, I couldn't reproduce the regression locally.

[dgl-bot]

Commit ID: 204d7acbc774e1ab0af69b00201f7724f8da11fc

Build ID: 2

Status: ✅ CI test succeeded.

Report path: link

Full logs path: link