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RubyIO needs allocation-free read and write paths #6589

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headius opened this issue Mar 1, 2021 · 1 comment
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RubyIO needs allocation-free read and write paths #6589

headius opened this issue Mar 1, 2021 · 1 comment
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core performance
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JRuby 9.3.0.0

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@headius
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headius commented Mar 1, 2021

Currently there is no way to read from or write to a RubyIO without creating a RubyString and accompanying ByteList. Meanwhile we have many places where we want to write a ByteList or even just a byte[] with a given encoding, such as IOOutputStream or the copy_stream logic for non-files.

We should build and use read and write paths that accept at least ByteList and ideally byte[], start, length, encoding to avoid allocation altogether.

This might be a good beginner to intermediate task for an external contributor.
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headius commented Mar 2, 2021

After attempting this myself, I'd say this is more of an advanced item... even for skilled Java folks.

PR coming.

@headius headius removed the beginner label Mar 2, 2021
headius added a commit to headius/jruby that referenced this issue Mar 2, 2021
@headius
Add a direct byte[] path for IO writes
236f7ba 
Several Java-based consumers of RubyIO write to it without having
a RubyString in hand, by wrapping incoming byte[] or ByteList.
This patch adds a write path that can accept unwrapped byte[] plus
encoding to reduce allocation and follow a fast path.

Users that hit this logic, mostly via IOOutputStream:

* The Psych ext when dumping to an IO
* For stdout and stderr streams provided by Ruby.getError/OutputStream
* By Marshal for dumping to a target IO or IO-like
* By GzipWriter for writing to a stream
* Anyone that calls to_outputstream on an IO

Part of work for jruby#6589
@headius headius mentioned this issue Mar 2, 2021
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@headius headius added this to the JRuby 9.3.0.0 milestone Mar 2, 2021
@headius headius closed this as completed Mar 2, 2021
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