On my Windows system memory.limit() reports a warning message that
'memory.limit()' is no longer supported
Not very helpful, I know.
Since you have only about 1 GB free, you can about double what's available by shutting down Chrome. You may need to shut it down in the task manager as sometimes just closing the Chrome window leaves pieces running. Past that, 8GB of memory is kind of light for doing heavy duty number crunching so consider whether adding more memory is worth it to save your time.
Also not very helpful, I know.