Of-late my laptop has been highly responsive …. as responsive as a sloth can be…
I mean you wouldn’t be expecting an Intel i5 Processor with 4GB Ram and 500GB hard disk making you go for a coffee break every time you had to build or compile your code.
I am sure many of you must have experienced some form of lag with your Ubuntu (I am using 11.10… But I did experience some form of lag with 10x series also).

So in this blog post I’ll be discussing some ways that you can follow to speed up your Ubuntu

1). Disable StartUp Apps the Smarter Way

Now when I started up StartUp Applications on a my Ubuntu 11.10 installation, all you can see are a mere 5-6 apps. Mine Actually had a whole lot more that were run at start up but are simply not shown like Yakuake, Gwibber, Desktop Sharing Sevrer, Bluetooth Manager etc. Ubuntu 11.04 was somewhat better where you could see most apps but still not all that would be let loose at startup. Using the following commands, I was able to enable all apps running at startup to be shown here.

cd /etc/xdg/autostart

sudo sed --in-place 's/NoDisplay=true/NoDisplay=false/g' *.desktop

Once that was done, restarting Startup Applications now showed all the apps that were running at startup. Just read the description once and decide whether you want to keep it at startup or not.

Startup Applications shown Initially

Startup Applications Now Showing Full List

rcconf is another tool that can be used but I found this method much more comprehensive and user friendly.

2). Swappiness is inversely proportional to Happiness

Swappiness is a property for the Linux Kernel that decides on how often to use the swap space. Most of the laptops today are equipped with 3-4 GB of Ram. So the principle of having double the swap space w.r.t to your memory size seems a bit outdated to me. Even though there was plenty of Ram available, my OS insisted on using the swap space, which in turn decreased responsiveness.
So I then moved on to change the swappiness value(Range:0-100, Default: 60)
Since I had a decent amount of RAM that could handle almost anything that was thrown at it, I decreased the swappiness quotient to 20.
To check the current swappiness value just type the following..

 cat /proc/sys/vm/swappiness 

Next to adjust the value swappiness value open

 sudo vim /etc/sysctl.conf 

Search for vm.swappiness and to change it to a desired value.If it is not present just add it to the end of the file. 10 is the figure that is mentioned on many forums, but I decided to play a bit safe and kept it a 20. Simply restart your system for the changes to take effect.

3). Reload Swap contents to Memory

Although I felt that decreasing the swappiness quotient did work for my computer, it is still possible that your computer swaps. This can hurt the multitasking performance of your system.
I found this script that you can use to to get the swap manually back into RAM.

err="not enough RAM to write swap back, nothing done"
mem=`free|grep Mem:|awk '{print $4}'`
swap=`free|grep Swap:|awk '{print $3}'`
test $mem -lt $swap && echo -e $err && exit 1
swapoff -a && swapon -a &&
exit 0

And place it at somwehere like

  /usr/local/sbin/swap2ram.sh 

Once you execute the script, it will transfer all your swap contents back to Memory, and free up your swap space. What it essentially does is turn off  swap space forcing everything back into RAM and turning it back on.

There are many more things that you can do to tweak up the speed of your computer, though I felt these 3 steps helped me a lot.
Hope this Helps