Remove use of removeAll(keepingCapacity:). #1699
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Motivation: As outlined in https://bugs.swift.org/browse/SR-13923, removeAll(keepingCapacity:) on Array has particularly negative performance when that Array is not uniquely referenced. In this case, in EmbeddedChannel, we _arrange_ to multiply reference it. This makes it swamp our HTTP/2 microbenchmarks, spending more cycles copying this buffer around than doing anything else. Modifications: - Just allocate a new buffer instead. Result: Much less copying.
Davidde94
approved these changes
Nov 30, 2020
PeterAdams-A
approved these changes
Dec 1, 2020
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Motivation:
As outlined in https://bugs.swift.org/browse/SR-13923,
removeAll(keepingCapacity:) on Array has particularly negative
performance when that Array is not uniquely referenced. In this case, in
EmbeddedChannel, we arrange to multiply reference it. This makes it
swamp our HTTP/2 microbenchmarks, spending more cycles copying this
buffer around than doing anything else.
Modifications:
Result:
Much less copying.