Poor performance in Protobuf map deserialization

[ricmf]

I'm running some benchmarks serializing objects to a RocksDB and deserializing them back. Deserialization is taking much longer than serialization. I profiled the program with jvisualvm and it seems the majority of CPU is spent on hashcode calls. On line 216 the lib deserializes the map entries into a linkedhashset, which for some reason takes the most CPU time in hashcode calls. Could this be replaced by a List deserializer since on the next line it everything is put into a map? If there are repeated MapEntry elements then their keys must be equal so associateBy would do the same.

kotlinx.serialization/formats/protobuf/commonMain/src/kotlinx/serialization/protobuf/internal/ProtobufDecoding.kt

Line 216 in 84d4af0

val setOfEntries = LinkedHashSetSerializer(mapEntrySerial).merge(this, oldSet)