bitcoin-cli very slow to respond to RPC calls (Raspberry Pi)

[Bitcoin]

bitcoin-cli very slow to respond to RPC calls (Raspberry Pi)

Running Bitcoin 0.11 on Raspberry Pi 2 (Quad core 900MHz 1GB RAM, 128GB Flash Drive for blockchain, 8GB SD Card for OS and software).

Blockchain is fully synced, 13 connections.
In htop, I see I'm around 700/862MB RAM, 1/99MB Swap. 1 processor is up around 90% but the other 3 are down in the <5% range.

I SSH into the pi (running bitcoind, no GUI) and some commands take forever to get a response. Sometimes getinfo or getpeerinfo will take 30-60 seconds to print out. gettxoutsetinfo takes way longer: almost ten minutes!! I don't see any resources being maxed out in htop during this time.

I know this is a low-power machine, maybe the UTXO set hash in the gettxoutsetingo command is what's specifically taking so long in that case.

Can I adjust any settings either in the RPi OS or bitcoin.conf to get snappier performance? Ideally I would like to run a few python scripts that use RPC, triggered by bitcoin's blocknotify=...

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