The stockpile which is estimated at just under $2.5 trillion is about 65% USD, 26% EUR, 5% GBP and 3% JPY according to Reuters quoting the China Securities Journal.
Even the moves in recent months to buy less Treasuries and more JGBs have had no impact whatsoever on the percentage allocation which begs the question, what would happen to the USD if China ever gets really serious about reducing its exposure to US assets.