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8276129: PretouchTask should page-align the chunk size #6204

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kimbarrett
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@kimbarrett kimbarrett commented Nov 2, 2021

Please review this change to PretouchTask to page-align the chunk size.
Aligning down is used because it's easy; aligning up would require dealing
with possible overflow or verifying that overflow isn't possible.

Testing:
mach5 tier1

Locally (linux-x64) java -version with pretouch task logging and various
chunk sizes, manually verifying the number of workers was as expected.


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Issue

  • JDK-8276129: PretouchTask should page-align the chunk size

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@bridgekeeper bridgekeeper bot commented Nov 2, 2021

👋 Welcome back kbarrett! 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 openjdk bot added the rfr label Nov 2, 2021
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@openjdk openjdk bot commented Nov 2, 2021

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

  • hotspot-gc

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

@openjdk openjdk bot added the hotspot-gc label Nov 2, 2021
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@mlbridge mlbridge bot commented Nov 2, 2021

Webrevs

stefank
stefank approved these changes Nov 2, 2021
// Chunk size should be at least (unmodified) page size as using multiple threads
// pretouch on a single page can decrease performance.
size_t chunk_size = MAX2(PretouchTask::chunk_size(), page_size);
// Page-align the chunk size, so if start_address is also page-aligned (as
// is common) then there won't be any pages shared by multiple chunks.
chunk_size = align_down(chunk_size, page_size);
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@stefank stefank Nov 2, 2021

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This looks like a place where align_down_bounded could be used. Something like this:

size_t chunk_size = align_down_bounded(PretouchTask::chunk_size(), page_size);

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@kimbarrett kimbarrett Nov 5, 2021

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I either forgot about or never noticed that function. Changed to use it.

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@openjdk openjdk bot commented Nov 2, 2021

@kimbarrett 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:

8276129: PretouchTask should page-align the chunk size

Reviewed-by: stefank, tschatzl

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

  • a472433: 8276572: Fake libsyslookup.so library causes tooling issues

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@tschatzl tschatzl left a comment

Lgtm independent of whether you want to incorporate @stefank 's suggestion.

stefank
stefank approved these changes Nov 5, 2021
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@kimbarrett kimbarrett commented Nov 5, 2021

Thanks @stefank and @tschatzl for reviews.

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@kimbarrett kimbarrett commented Nov 5, 2021

/integrate

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@openjdk openjdk bot commented Nov 5, 2021

Going to push as commit 0e0dd33.
Since your change was applied there has been 1 commit pushed to the master branch:

  • a472433: 8276572: Fake libsyslookup.so library causes tooling issues

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot closed this Nov 5, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels Nov 5, 2021
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@openjdk openjdk bot commented Nov 5, 2021

@kimbarrett Pushed as commit 0e0dd33.

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

@kimbarrett kimbarrett deleted the align_pretouch_chunk_size branch Nov 5, 2021
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