From: ctwilson@rock.concert.net (Charles T Wilson -- Personal Account) Subject: Re: Thrashing - how to quantify Date: 12 Sep 1993 19:10:15 GMT
In article <26v9m5$spd@frigate.doc.ic.ac.uk> rj3@motmot.doc.ic.ac.uk (Richard William Jones) writes:
>When I run gcc on my machine with 5 megs of real memory installed, it
>seems to run very slowly and swap frequently ... So it's probably thrashing ...
Thrashing occurs when the primary activity of the OS is dealing with page
faults..ie, servicing requests for the necessary pieces/parts of the
executable(s) and data. Even though your system is not necessarily under
a heavy load, very little seems to happen. A lot a swapping does not
necessarily mean your system is thrashing, which is not to say that you
wouldn't want more ram. I can't say about your situation from here. I'd
be more inclined to believe that you're having problems with your ram
(assuming you're not also running X at the same time...a heavy load for
5 megs of ram).
>What I need is a way to quantify exactly how much time is spent swapping
>in/out and how much is spent running the program. This way I can start
>to tune the system. The obvious choice is ps, but this doesn't seem to give
>the info I need, and really I'm stuck. Does anyone have any ideas?
I don't think I've heard of a need for more than 16 megs. I run fairly
well with 8 megs physical and 16 megs swap, which includes X. I plan
on getting more, but I'm not exactly suffering from excessive swapping.
>Secondly, how much real memory am I going to need? This stuff is expensive,
>and I think my only option is to go for the full 16+4 megs (I've only got
>8 slots, with 4+1 config at the moment). This will cost more than I can bear
>at the moment. Is there another solution.
I'd start by pulling that bank of 256K simms out just to see what happens.
If you run about the same (or even speed up), then those simms are either
defective or not entirely compatible the other bank of simms. Like many
other OS's, Linux uses ram more thoroughly ( poor choice of words, but the
right ones won't come to me) than something like DOS, and will 'separate
the wheat from the chaff', so to speak.
I hope vendors aren't trying to make hay over the fire at that resin factory;
it was back in operation in at least partial capacity about two weeks after
the accident. Just previous to this, 70 ns RAM (what I use) was averaging
about $35/meg from most of the vendors I pay attention to. Has this changed
very much? Just as an example of what can happen, a local PC show had
vendors selling 60-70 ns RAM at anywhere from $40 - $95 per meg just after the
fire; at least that's what I was personally aware of.
-- /-----------------------------------------------------------------------\ | Tom Wilson | "I can't complain, but sometimes | | ctwilson@rock.concert.net | I still do." | | | -Joe Walsh |