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Go Optimization Guide

(goperf.dev)
480 points jedeusus | 2 comments | 31 Mar 25 20:29 UTC | HN request time: 0s | source
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dennis-tra ◴[01 Apr 25 12:15 UTC] No.43545831[source]▶
Can someone explain to me why the compiler can’t do struct-field-alignment? This feels like something that can easily be automated.
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CamouflagedKiwi ◴[01 Apr 25 12:20 UTC] No.43545865[source]▶
Because the order of fields can be significant. It's very relevant for syscalls, and is observable via the reflect package; it'd be strange if the field order was arbitrarily changed (and might change further between releases).

I assume the thinking was that this is pretty easy to optimise if you care, and if it's on by default there'd then have to be some opt-out which there isn't a good mechanism for.

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1. 9rx ◴[01 Apr 25 17:56 UTC] No.43549682[source]▶
> and if it's on by default there'd then have to be some opt-out which there isn't a good mechanism for.

Good is subjective, but the mechanism is something already implemented: https://pkg.go.dev/structs#HostLayout

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2. CamouflagedKiwi ◴[02 Apr 25 13:51 UTC] No.43556694[source]▶
Oh interesting, I've not encountered that before - I suppose because it is currently the default behaviour.

What I was hoping not to find (and fortunately didn't!) was one of Go's magical syntactic comments.