Fix problems associated with analyzer timing#24564
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sharwell merged 3 commits intodotnet:dev15.6.xfrom Feb 2, 2018
Merged
Fix problems associated with analyzer timing#24564sharwell merged 3 commits intodotnet:dev15.6.xfrom
sharwell merged 3 commits intodotnet:dev15.6.xfrom
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mavasani
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Jan 31, 2018
heejaechang
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Jan 31, 2018
jasonmalinowski
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Feb 1, 2018
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Who would have thought timing is so hard. Nice find!
| private readonly Func<Diagnostic, DiagnosticAnalyzer, Compilation, CancellationToken, bool> _shouldSuppressGeneratedCodeDiagnostic; | ||
| private readonly Func<SyntaxTree, TextSpan, bool> _isGeneratedCodeLocation; | ||
| private readonly ConcurrentDictionary<DiagnosticAnalyzer, TimeSpan> _analyzerExecutionTimeMapOpt; | ||
| private readonly ConcurrentDictionary<DiagnosticAnalyzer, StrongBox<long>> _analyzerExecutionTimeMapOpt; |
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Nit: add a comment to say what unit this is in now that we've lost the TimeSpan. (I normally hate any non-TimeSpan but obviously in this case you're doing it for a Good Reason™.)
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I normally hate any non-TimeSpan...
Me too.
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Approved to merge via Link |
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Customer scenario
A customer runs the compiler with analyzer timing enabled (either through the API or with a compiler flag on the command line). The timing operations incur substantial overhead on concurrent builds, and when one or more analyzers allocates large amounts of data, the timing results are inaccurate.
Bugs this fixes
DevDiv 560657 (internal mirror of this pull request)
Workarounds, if any
Risk
Low.
Performance impact
Performance for intense analyzer scenarios can be improved by 20%. In addition, timing error rates of over 150% were observed for some analyzers.
Is this a regression from a previous update?
No, but the work to reduce overhead in this scenario revealed another problem at the same location. This bug is limiting our ability to observe the expected gains from previous work.
Root cause analysis
The previous work in this area was focused on allocation reductions (#23582), which were achieved as expected by #23621. The problem corrected by this pull request is a CPU time problem revealed by profiling execution times (#23583).
How was the bug found?
Profiling per #23583.
Test documentation updated?
N/A