context: allow pre-allocation of valueCtx #42329
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It was my impression that CL 196521 modified Meaning, you should be able to write this code: type myValueContext struct {
context.Context
key interface{}
value *SomeValue
}
func (v myValueContext) Value(key interface{}) interface{} {
if key == v.key {
return v.value
}
return v.Context.Value(key)
)And it only incur a single allocation (ignoring my placeholder types). On a |
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Ah, awesome! Yeah that does it. I had checked the source at https://golang.org/src/context/context.go?s=8419:8483#L222 but I guess it's outdated. |
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In various CockroachDB workloads,
context.WithValueshows up as a few percentage points in profiles (similar to any other object allocation). In many cases, we also allocate an object for the value that is associated with the context. We would like to consolidate these allocations by embeddingvalueCtxinside a bigger struct, so that we can allocate both objects together.Note that we can't have our own implementation of
Contextwithout losing some efficiency becauseparentCancelCtxwon't be aware of it.My proposal is to export the
valueCtxtype (or an alias) and provide a method orWithValuevariant to initialize it. Would this kind of addition to the API be acceptable? (I can post the change if yes)The text was updated successfully, but these errors were encountered: