My guess is that when you measure, an arena is not worth the trouble when you run a generational GC, which essentially uses an arena for the eden space already. And if you have an arena, it's probably very short lived and would otherwise live entirely in eden.

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jeffrallen 3 days ago | parent [-]

Go's GC is not generational.

	▲	raggi 3 days ago \| parent [-]
		It's not, but joining the two comments together sync.Pool is often close to what you want for a subset of cases, and it's sort of a locality biased generational storage (without actually providing you strong long-term guarantees that it is that).