Is it possible to reserve exact amount of space for the indexing and virtual memory?
As SSDs age, it takes more and more work for them to store data.  This is only made worse by having less than 1GB of space available.  In my experience (with a 2010 Macbook Air, with the 250GB SSD), performance GREATLY improved when I had >10% free space.  

Do what you can to give your computer some breathing room!  Delete some files now!

Here's a classic article on how SSDs work.  Probably TMI, but...
   http://arstechnica.com/information-technology/2012/06/inside-the-ssd-revolution-how-solid-state-disks-really-work/