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I have 1GB of RAM, and when I run NetBeans and Firefox, they get about 300MB of RAM. At some point, the system becomes very slow, probably 100 times slower than normal, switching windows (Alt+Tab) becomes a huge task and the computer is practically useless. This is probably the moment when it starts to swap.

Two questions:

  1. According to images provided, where has all the RAM gone? When I calculate all the processes memory, it is far smaller then 1GB.
  2. Is it normal for system to become 100 times slower when the RAM is full and using swap space?

On another computer with 4GB of RAM I have no problems.

enter image description here enter image description here

Update: I added 2GB of RAM, now I have 3GB. Anyone who wants to use heavy apps with 1GB on Unity, I don't think it's going to work. Works fine on an empty desktop :)

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Main memory access time is in the order of nanoseconds, hard disk drive access time is in the order of milliseconds. You should rather wonder that it isn't (quite) a million times slower when it's swapping. –  Chris Morgan Jun 29 '11 at 22:49
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4 Answers

up vote 12 down vote accepted
  1. Under View make sure you have selected All Processes :

    enter image description here

  2. Yes, that's normal. Swap space on a hard drive is muuuuuch slower than RAM.

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Thanks for your answer. Yes, there are more processes, apache for example have a couple of them. Still looks like sum is not greater then 700MB, but there are a lot of them having N/A for memmory. In general there are a lot of them, more then 100! Is that normal? So, if I want to use this heavy apps, I need to buy more RAM? :) –  umpirsky May 22 '11 at 17:48
    
I had the similar problem. Plus, in "system monitor" you don't see buffers and and caches. To see this, go to terminal and say free -m. You can use Chromium instead of firefox, it might use ram better (it WILL release ram after you close tab, unlike Firefox) –  gsedej May 22 '11 at 18:44
    
Heh, I will add more RAM, but I just wanted to check if this is normal behaviour. I didn't expect so drastic slow down when out of memory. –  umpirsky May 22 '11 at 19:35
    
Remember that an integrated video card will likely have some of your RAM allocated to it as well, leaving you with less than 1GB to start with. –  Nerdfest May 28 '11 at 14:24
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Did you encrypt your home folder by any chance? I did and it also created an encrypted swap (it only does so on when installing ubuntu).

That swap besides slowing my boot time seems to be extremely slow: For compassion I used a Pentium 4, 1GB of RAM as my main PC (home encrypted but not swap I think) and never swapping was so bad like now that I switched to a Core I5 laptop with 4GB of RAM.

I need to use swap when working with PDF's (most related programs seem to forget that /tmp exists..)

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I suggest you take a look at this article https://help.ubuntu.com/community/SwapFaq you can tune your swap usage here (make it use swap later/earlier)

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Nice, thank you. –  umpirsky May 28 '11 at 12:09
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Yes, it's normal for your system to be extremely slow, or entirely unusable when your RAM is full (Trust me, I only have 2GB of RAM).

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I don't see the purpose of having swap partition then :) –  umpirsky May 23 '11 at 8:13
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@umpirsky: if you had no swap, Linux will run OOM kill and processes will be killed. If you're "lucky", it's just Firefox with some unimportant websites. If you're unlucy, it's Netbeans with your unsaved work. –  Lekensteyn May 23 '11 at 17:55
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@Lekensteyn I know :) That was a joke, because system is not usable when you are out of RAM. I'm not sure that's the case with Windows (I don't like it anyway). –  umpirsky May 23 '11 at 18:37
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