Previously system became unresponsive when RAM usage reached around %70. It was because of massive disk I/O operation, presumably to swap disk. I tried to tweak swapiness factor and it didn't affect anything at all on both sides of the extreme. I decided to delete the swap partition altogether, since my system has 4GB RAM. The swap partition was about 6GB. It is yet no difference. It seems in whatsoever configuration, %30 of memory should always be free. This is not a space rocket command and control system, so I don't understand this cautious policy. Can anyone please explain? Is there any other setting I could tweak to get the bar of memory usage up to say %95?