High memory usage

[enertom]

The memory usage is very high. (about 16Gb)

Start with:
--cache-size=512 --jsonrpc-port=60000 --ws-port=60001 --jsonrpc-interface all --jsonrpc-server-threads=8 --ws-interface all --db-compaction=ssd --pruning fast --mode active -l sync=info --no-warp --pruning-history=1000000

htop command:
https://pix.toile-libre.org/upload/original/1593625288.png

• OpenEthereum version: Parity-Ethereum/v2.7.2-stable-2662d19-20200206/x86_64-unknown-linux-gnu/rustc1.41.0
• Operating system: Linux
• Installation: docker
• Fully synchronized: yes
• Network: ethereum
• Restarted: no

[jiangxjcn]

set
--pruning-history=1000000
need large memory.
(i set pruning-history=24000, and it will use around 70GB memory)

[adria0]

Duplicated of https://github.com/openethereum/openethereum/issues/11760