slow Kubuntu 14.04

[nicrnicr]

Dear all,

Since I use again my Kubuntu 14.04 on an ACER Aspire 5750G, I find it very slow. I usually have to wait 15-60 seconds between a click on the mouse and its effect and the windows are often very badly shown.
Please could you help me to speed it?
This may help you:

alfred@alfred-Aspire-5750G:~$ df -h
Dateisystem    Größe Benutzt Verf. Verw% Eingehängt auf
udev            3,9G    4,0K  3,9G    1% /dev
tmpfs           784M    1,2M  783M    1% /run
/dev/sda3       286G    254G   18G   94% /
none            4,0K       0  4,0K    0% /sys/fs/cgroup
none            5,0M       0  5,0M    0% /run/lock
none            3,9G    120M  3,8G    4% /run/shm
none            100M     20K  100M    1% /run/user
alfred@alfred-Aspire-5750G:~$

alfred@alfred-Aspire-5750G:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sda3 during installation
UUID=2afde356-50bd-425d-892e-6e4ba30d99c1 /               ext4    errors=remount-ro 0       1
# swap was on /dev/sda5 during installation
UUID=686a675f-922f-48cf-803a-11b3604bc359 none            swap    sw              0       0
alfred@alfred-Aspire-5750G:~$

You can also find enclosed a picture of the CPU use.

[Snowhog]

Your system (you have 14.04 installed on one single partition) is very full:

/dev/sda3 286G 254G 18G 94% /

Specifically, the data above shows that you are using 94% of your 286G.

That alone doesn't necessarily explain your slowness, but it is going to effect operation of your system eventually.

When is the last time you cleaned up your system; removed downloaded package updates; removed older installed kernels; etc.?

[nicrnicr]

Thank you SnowHog for your answer :-)
I*deleted 10 G, three packages with autoremove and the thumbnail cache (through https://sites.google.com/site/easyli...sproject/clean). Furthermore, I have no more than one unused Kernel. I restarted Kubuntu and it's now running well. I hope it will keep on running fast. Wether or not. I will write it.

[Qqmike]

Some of us here have used the cleaner called Bleachbit. It is in the repositories (you can install it using Muon). I use it without any issues on my 14.04. I haven't checked the documentation lately to see what's going on with it lately, but it is something to consider.

[nicrnicr]

Thank you Qqmike for your comment.
My computer becomes slow after approx. 6 hours during which it has been put at least 3 times in stand-by.

[dequire]

Another great tool used by some around here is ucaresystem-core. You can read more about it here. In essence, it's a simple script file that performs a series of maintenance-type tasks, as outlined in the accompanying screenshot. I've used it on all installs since I found out about it and can't really recommend it enough. Additionally, myself and others here have perused the script and can attest to it's simplicity and thoroughness.