unix RAM usage (Was: Re: OOo background color - Re: [GNHLUG] MerriLUG Nashua, Thur 20 Sep, OpenOffice Styles - for groff fans and real people too)

[Bill McGonigle]

On Sep 24, 2007, at 11:34, Tom Buskey wrote:

> Eight
> Megabytes
> And
> Constantly
> Swapping
>
> Kinda outdated when firefox takes 241MB and systems generally don't  
> swap.

So that brings up a question for those who understand unix: if I have  
an emacs running, e.g.:

     PID COMMAND      %CPU   TIME   #TH #PRTS #MREGS RPRVT  RSHRD   
RSIZE  VSIZE
   29806 emacs-i386   0.0%  0:00.03   1    15    25  1.15M  3.75M   
2.84M  47.0M

the virtual size is 47M, but the shared and resident sizes rarely  
change from their combined 8MB (it's true! - I aggravated our  
sysadmin in college by running emacs on an 8MB machine (that served  
the whole department) - it took 8MB then as well).

I understand that there's stuff in that 47MB space that might need to  
be swapped in, but since it so rarely does, it is all just pre- 
allocated buffers that are never used?  There's a concept here I  
don't really understand, apparently.

Firefox is behaving similarly:

    7834 firefox-bi   0.7% 59:43.62  14   195  1551   247M  52.2M    
275M   567M

and I've been told the delta is largely [image,DOM,history] cache.   
But I would (naively?) assume emacs can allocate more memory on the  
fly, so my theory doesn't make very much sense.

-Bill

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