This is really annoying. But looking at the output you have, it appears that restic is/was using 1.5GB memory and wanted to allocate another 800KB. If you have 8 GB on that machine, you must have something else that’s hogging a lot of memory?
Everything is relative so I’m not going to say that 1.5GB of memory is a low requirement for a backup program, but it is what it is currently. I don’t feel it’s insanely high either, for a repo of that size. Surely we’d like to make it less, but people with actual coding skills need to attend that.
Can you show us the output of free right before you run restic, and also an updated output from it so we can see the amounts of memory at the same point in time?