How to show unread mails on gmail?

I was wonder if there is any way out to show only unread mails in Gmail?
I have many unread mails(to do tasks actually :P) that I marked as unread.

In case there is no way out,
Perhaps, unread can be a default system label for all unread mails. ;)

How to drop caches in Linux ?

Symptoms:
If the system is eating up lot of RAM eventually making the system slow then try freeing up the cache memory.

Before freeing up the cache, running sync flushes all the file system buffers.
In root, run the following commands:

To free pagecache, inodes and dentries:
root@inferno: echo 3 > /proc/sys/vm/drop_caches

To free only the pagecache,
root@inferno: echo 1 > /proc/sys/vm/drop_caches

To free only the dentries
root@inferno: echo 2 > /proc/sys/vm/drop_caches