8353923: (fs) Further improve performance of URI -> Path conversion (win)

[bplb]

If the path portion of a URI permits, then simply replace all '\\' with '/' instead of completely parsing the path.

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Issue

• JDK-8353923: (fs) Further improve performance of URI -> Path conversion (win) (Bug - P4)

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[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (325abb62)
• 00: Full (3bd3e2a9)

[bplb]

Benchmark testing of URI-to-Path conversion on Windows gives these results:

URI	Throughput Change (%)
file:/C:/Users/bpb/git/foo/bar/classes/gus/dir/	+63.96
file:/C:/Users/bpb/git/foo/bar/classes/gus/dir	+61.19
file:/C:/Users/bpb/git/foo/bar/classes//gus/dir/	-4.19
file:/C:/Users/bpb/git/foo/bar/classes//gus/dir	-2.21

For URIs having a path to which the optimization applies, the throughput increase is nearly two-thirds. For URIs which are not so amenable, there is a small throughput decrease of less than 5%. URIs which have a UNC path component are not affected.

So the question is whether a substantial throughput increase for susceptible absolute drive paths is worth a small but non-zero throughput decrease for other path components.

[AlanBateman]

Is it possible to add a JMH benchmark to the PR?

[bplb]

Is it possible to add a JMH benchmark to the PR?

Yes, I was intending to do that.

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[bplb]

continue;

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[bplb]

/touch

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