docs/feature: Nested ReturnToVTPool()

[coxley]

docs/feature: Nested ReturnToVTPool()

[coxley]

Ah, I see this is mentioned in #8 and #63.

@nockty: [We] need further information to tackle this issue. Namely, a benchmark showing that individually pooling objects can be more performant in certain scenarios.

Not sure if it helps, but in my use-case I can't decode the entire object at once.

The children objects reside as bytes in a ton of BigTable cells. The parent is only initialized after the children have finished decoding in-full. Pooling the children makes sense for us because these decodes have to be done separately as each result is read.

The best place to release everything is once the parent is no longer needed — thus recursive return being ideal for us.

[vmg]

The finalizers approach is IMO out of the question because they perform horribly in Go. I do agree this is a bit of a footgun in the pooling API, and it may not be enough to clarify the documentation. I think the recursive release would be the safest API we can provide, but I get the feeling it will require quite a bit of code. 😓

[coxley]

To clarify, I wasn't suggesting those steps as part of the API. Just the only levers users currently have available. :)

[HALO-04]

Hi @vmg , I'm also interested in this topic. Can you please help me resolve my two small doubts?

1. Does the phrase recursive release means generating code liking this:

func (m *Foo) ResetVT() {
	for _, mm := range m.Bars {
		// mm.ResetVT()
                mm.ReturnToVTPool()        // if mm is poolable, use ReturnToVTPool instead of ResetVT
	}
	f0 := m.Bars[:0]
	m.Reset()
	m.Bars = f0
}

2. Will pooling for map type be supported in the future? I think this might bring the benefits like reusing slice

message Foo {
  option (vtproto.mempool) = true;
  map<int64, Bar>  barsMap = 1;
}

message Bar {
  option (vtproto.mempool) = true;
}

func (m *Foo) ResetVT() {
        keysToDelete := []int64{}
	for key, value := range m.BarsMap {
                value.ReturnToVTPool()                                       // only put the values in sync.Pool
                keysToDelete = append(keysToDelete, key)
	}
        for _, key := range keysToDelete {
                delete(m.BarsMap, key)
        }
	f0 := m.BarsMap
	m.Reset()
	m.BarsMap = f0
}