Write VarInt as fast as possible by unrolling the loop#363
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AkmalFairuz wants to merge 1 commit intoSandertv:masterfrom
Open
Write VarInt as fast as possible by unrolling the loop#363AkmalFairuz wants to merge 1 commit intoSandertv:masterfrom
AkmalFairuz wants to merge 1 commit intoSandertv:masterfrom
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I understand your point of making varints as fast as possible, but I have quite some concerns over the worthiness of doing this. The performance gains are minimal for the majority of the varints (0.3-0.4ns/varint for 1/2 bytes) and the code for a relatively simple feature blows up to over 400 lines. That does not sound like a compromise worth making, especially given the fact that varints, to my knowledge, are not a performance bottleneck in the first place. |
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Description
VarInt is a hot path in the Minecraft Bedrock network protocol, so we need to make it as fast as possible. After some testing and benchmarking, I found that unrolling the loop makes VarInt writes faster. In most cases, we usually write 1-2-byte VarInts. For 2-byte VarInts, the speed is about the same, but for 1-byte VarInts it’s around 13% faster. As you can see from the benchmark results, writing VarInts of 3 bytes or more becomes significantly faster!.
Test & Benchmark Code: https://gist.github.com/AkmalFairuz/daadc682603ae5f1d0f77b7fd748853e
Inspired by: https://steinborn.me/posts/performance/how-fast-can-you-write-a-varint/
Benchmark Result