Ask Ubuntu is a question and answer site for Ubuntu users and developers. It's 100% free.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Why is there a huge difference between the outputs' of top command and the system monitor when both programs were run at the same time. Please find attached is the screen shot showing the huge difference:-

See the Ram usage, in GUI it just shows 1.1G whereas in CLI the usgage climbs upto 3.2G

Is this a bug?

share|improve this question
Difference in terms of memory usage, processes running?? Choose view > all processes to show them all in System Monitor. See this discussion also – user76204 Aug 16 '12 at 16:52
I think the link I quoted should help as that is about RAM usage. I find htop, which is in the repositories, is easier to use than top and gives clearer results. – user76204 Aug 16 '12 at 17:00
up vote 3 down vote accepted

If you are referring to RAM usage, it is because system monitor does not include buffers and caching, just actual Ram used to run applications, top is slightly confusing because it does not obviously show disk usage after buffers / caching. Try using the following command :

free -m

See the image below, and note that the second line of free -m indicates available Ram, whilst the first line indicates actual Ram usage including disk caching.

enter image description here

I would recommend installing and using htop as it is better and simpler than top in my opinion.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.