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UDP reads allocate extra memory through lazy string copying #5157

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andrewvc opened this issue May 3, 2018 · 2 comments
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UDP reads allocate extra memory through lazy string copying #5157

andrewvc opened this issue May 3, 2018 · 2 comments
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@andrewvc
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andrewvc commented May 3, 2018

Using UDP#recvfrom_nonblock(buffer_size) we've noticed that the underlying strings are the size of the buffer always, regardless of the actual message size. The strings are accurate, but rather than actually truncating the underlying byte[] JRuby simply adjusts the underlying length of the string.

When performing a large number of reads off a UDP socket with a 64k buffer size this results in a large amount of unnecessary heap being allocated.

Tested with JRuby version 9.1.13.0
@andrewvc andrewvc mentioned this issue May 3, 2018
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@andrewvc
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andrewvc commented May 3, 2018

I should mention, one workaround here is to invoke String#b, then force encode the string. That seems to force truncation.

@andrewvc
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andrewvc commented May 3, 2018

Closing as this is a dupe of #5148

@andrewvc andrewvc closed this as completed May 3, 2018
@enebo enebo added this to the Invalid or Duplicate milestone May 24, 2018
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