Ubuntu Eats My Memory

[Arun]

Ok,
Thanks for all the replies. That is the reason why I do not see any memory
being used by any processes.


On 10/17/07, Joris Dobbelsteen <Joris at familiedobbelsteen.nl> wrote:
>
> >-----Original Message-----
> >From: ubuntu-users-bounces at lists.ubuntu.com
> >[mailto:ubuntu-users-bounces at lists.ubuntu.com] On Behalf Of
> >Brian Fahrlander
> >Sent: woensdag 17 oktober 2007 16:09
> >To: Ubuntu user technical support,not for general discussions
> >Subject: Re: Ubuntu Eats My Memory
> >
> >Ruben Laban wrote:
> >
> >> In your output of top it shows "1383868k cached". So basicly there's
> >> roughly 1.3GB of memory 'in use' as cache. If you'd use the command
> >> "free -m", you'd see that the cache isn't 'really' using the memory.
> >> Cache memory can be freed when a program needs it.
> >
> >     Yeah, the Linux memory system is fabulous. I once was
> >working with a  set of full-page newspaper-sized JPGs. Each
> >one was about 10M or more, and there were 200 or so on the
> >volume.  I wanted to copy them someplace; I was watching TV at
> >the time, and didn't realize how much memory this was going to take.
> >
> [snip]
> >
> >     Linux actually _uses_ memory; whatever's just sitting
> >around, it uses the space to hold library routines and things,
> >ready at a millisecond's notice to dump them and make room for
> >'real' storage.
> >It's a very sweet design!
>
> Your assumptions made are not true (in very nice working). They indicate
> complete lack of understanding how the virtual memory is implemented in
> any modern operating system (Windows/Linux/*BSD/Solaris/...).
>
> What you are missing is the different INTERPRETATIONS you get when you
> ask how much memory "is used".
>
> For Windows (NT4/2000/XP) you get the amount of memory actually in use
> by applications + kernel. This figure doesn't represent the amount of
> file cache in use, which is indicated in the task manager under the
> "Performance" tab as "System Cache". In fact, you can have a situation
> where application+kernel + file-cache is larger than the total memory
> available (hint: swap).
> I don't know how with Vista the value is interpreted.
>
> For Linux the used memory is interpreted as memory that is either used
> by the kernel, application or as file cache. So the value, while it has
> the same name, means something completely different. In fact, the notion
> of 'used' is Linux might be quite confusing to some users. Nevertheless,
> I personally don't call the overcommit handling in Linux a 'sweet
> design' (I would rather nominate NetBSD).
>
> If you want better figures for Linux, try the "free" command. You will
> get the following output:
> ===
>             total       used       free     shared    buffers
> cached
> Mem:        256232     249192       7040          0         32
> 50076
> -/+ buffers/cache:     199084      57148
> Swap:       248996      23868     225128
> ===
>
> I won't even vouch that any of these values are equivalent to the value
> Windows provides. My best guess is that Windows "Used" = Linux "Used -
> buffers - cached + swap_used". Also, Windows "System Cache" is
> equivalent to Linux "Cached". Also, there is still the difference
> between memory that is reserved/allocated by applications and memory
> that is actually used.
>
> A possible notable difference between Linux and Windows is that Linux is
> much more aggressive in moving application to the swap space, in order
> to keep its file cache as large as possible. Obviously both are not
> ideal, but rather offer a different trade-off.
>
>
> - Joris
>
>
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-- 
Thanks
Arun George
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