presto-main/src/main/java/io/prestosql/operator/SimplePagesHashStrategy.java/SimplePagesHashStrategy/getSizeInBytes
class SimplePagesHashStrategy:    @Override
    public long getSizeInBytes()
    {
        return INSTANCE_SIZE + channels.stream()
                .flatMap(List::stream)
                .mapToLong(Block::getRetainedSizeInBytes)
                .sum();
    }