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[SR-9907] DataAppendDataLargeToLarge benchmark is unstable #52313

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eeckstein opened this issue Feb 11, 2019 · 4 comments
Closed

[SR-9907] DataAppendDataLargeToLarge benchmark is unstable #52313

eeckstein opened this issue Feb 11, 2019 · 4 comments
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@palimondo
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself

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@eeckstein
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Previous ID SR-9907
Radar None
Original Reporter @eeckstein
Type Bug
Status Closed
Resolution Done

Attachment: Download

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug
Assignee @palimondo
Priority Medium

md5: aafd9c21b73a0959141b6a2153ce8d03

relates to:

  • SR-9911 Data.append - high performance fluctuation

Issue Description:

no-op changes report a performance difference of 1.35x.

For example, see the benchmark run in #22341
@eeckstein
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Pavol, would you be able to take a look?

@palimondo
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Mannequin

palimondo mannequin commented Feb 11, 2019

I’ll try… I’ve seen this jumping up and down a lot. But I suspect it is an artifact of Data’s implementation. I’ll report tomorrow.

@palimondo
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palimondo mannequin commented Feb 12, 2019

OK, so DataAppendDataLargeToLarge has multimodal runtimes (2 major, and 2 minor modes). There is 36% difference between the major modes. It has about 3:10 or 4:12 chance of not hitting the minimal mode.

This multimodal behavior of Data should be looked at separately. But I think the most robust way to fix sporadic reports of this false change is to bump unchanged_lenght_count comparison in run_smoke_bench from 5 to 10. Would you agree, @eeckstein?

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palimondo mannequin commented Feb 12, 2019

PR #22546

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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@palimondo palimondo

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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself
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@eeckstein