I dont know,
gmaxwell DnT suggested it when
I someone else had problems with memory
and it worked like a charm. Let me dig that thread up. See the thread linked below[1]. I remember that it reduced the amount of RAM my node needs, while I had problems with 2 GB before.
free -m:
total used free shared buffers cached
Mem: 2048 2018 29 5 0 1592
-/+ buffers/cache: 425 1622
Swap: 0 0 0
[1]
https://bitcointalk.org/index.php?topic=659040.0