presto-main/src/main/java/io/prestosql/operator/exchange/PageReference.java/PageReference/removePage
class PageReference:    public Page removePage()
    {
        int referenceCount = this.referenceCount.decrementAndGet();
        checkArgument(referenceCount >= 0, "Page reference count is negative");
        if (referenceCount == 0) {
            onFree.run();
        }
        return page;
    }