LXC Export RAM Usage/Threading

It looks like the LXD process grows in relation to the size of a container when exporting. Is there any way to flush it to disk in 1GB increments for larger root filesystems?

I have a modest server with 24GB of RAM and I was surprised to see it thrashing swap when I was backing up a 16+ GB container.

Additionally, xz is spawning a single thread to do the compression which is a huge bottleneck, options for compression would be appreciated.