The problem was that an overload of CodedOutputStream.newInstance
without size uses 4000 as a default value, thus allocating
a 4k-sized byte array.
At the same time the array remained effectively unused
in the most cases since it only used for storing data
for unknown fields.
Because such arrays are being created for each read of
protobuf message, during compilation of IntelliJ project
it was producing 25% of redundant memory traffic.
Of course these arrays were all in the young gen, but still
they have some effect on GC
Denis Zharkov
63c5d85cf4