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[fwd from cameron] Re: Why is system linux so slow?

Actually, you have to be carefull when using free to measure how much
memory you got free.  If I had 512 MB of memory on my system, but only
really needed 32 MB, Linux would use the remaining 480MB as a disk cache.
Therefore, free would report only a few kbytes of free memory.  

This is done automatically and dinamically.  If on that fictional machine,
I suddenly fired up a copy of Bochs telling it to use 256 MB, Linux will
release those 256 MB from the cache and give it to Bochs.  So, I would be
using 290 or so MB with my apps, and 220 or something as a disk cache.
When Bochs quits, its now freed memory will be restored to the disk cache.

Don't assume that because free tells you that you have only 53k free that
your software is eating up all your memory.  It just might be the cache.



Victor R. Rivarola                These words are mine and mine only, they
victor sisteco com py             do not necessarily represent the views
Unix Specialist                   of my employer.
SISTECO Paraguay S.R.L.

On Tue, 14 Jul 1998, Cameron Simpson wrote:

> Linux Idiot <esoteric denali atlnet com> writes:
> | > > > Netscape is veerrrry slow in loading, Emacs makes the computer thrash
> | > > > getting loaded in my NEC Pentium 100mhz with 24mb RAM and 25mb Linux Swap,
> | > > > etc.  Things take a long time to load, and thrash a lot.
> | > >Linux Idiot wrote:
> | > > I would increase my swap space.  What does 'free' show you have
> | > > available memory wise?
> More swap will NOT help. What do you think "thrash" means? It means
> spending all the time paging data back and forth between RAM and swap.
> It can only be helped by increasing RAM or decreasing working set
> (a.k.a. resident set) size, typically by running fewer programs at once
> or less memory hungry versions of programs.
> Find out what's running, and what wants lots of RAM. (Clue: check out
> the RSS column of a verbose ps listing.) Those are the target apps to
> tune/discard/whatever.
> --
> Cameron Simpson, DoD#743        cs zip com au        http://www.zip.com.au/~cs/
> First snow, then silence.
> This thousand dollar screen dies
> so beautifully.
> - Haiku Error Messages http://www.salon1999.com/
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