[kde-solaris] swap space requirements [was: KDE 3.1.4 - Can't talk to klauncher]

[Stefan Teleman]

Rolf Sponsel wrote:

> Tell me; do you really think that I'll *have to* add another 0.5 GB
> swap space to my system when - if - I decide to add another 128MB?
> I do not - rather on the contrary (should I want reduce it) ;-)

Great! Please, reduce it! My only request is: please post your
/var/adm/messages after you do so. :-) If you can still use vi,
that is.

Yes, you do need to increase swap whenver you increase core RAM.
Especially for workstations which come with a small amount of core
RAM to begin with. Whether it should be done at 128MB or 256MB,
that's a matter of tolerance. But, 128MB RAM is significant enough
to warrant increasing swap, especially when you had very little swap
to begin with.

> "The most important factors in determining swap space size are the
>       requirements of the system's software applications. For example,
> large applications such as computer-aided-design simulators,
> database-management products, transaction monitors, and geologic
> analysis systems can consume as much as 200-1000 Mbytes of swap space."
> 
> ...
> 
> But, these large applications, I suppose, are to run in a desktop
> environment *and* none of the examples given in the general
> guidelines have swap space that is larger that the pysical memory
> (they're actually 1/4:th of the size of the physical memory).

Actually, database servers or geologic analysis systems usually run
on enterprise-class multiprocessor servers, not on desktops. The GUI
may run on desktops, but the engine runs on servers. These
servers can accomodate many GB RAM (8, 12GB or even more). And the
explanation for the swap to core ratio is: the amount of available
core RAM. That is, if you already have 8GB core RAM, you probably
don't need 24GB swap. You can probably do fine with only another 4GB,
just because the swapping will be minimal. Unless the software in use
requires extremely large (GB's worth of) data sets to be resident
in memory. Which many statistical analysis sytems do. What kind of data
sets would require such a thing ? For example: any type of Monte Carlo
simulation with let's say 250,000 paths on a set of 1000 30-year time
series with 3600 daily sample points. Then you need TONS of swap space.

> I really doubt that KDE should require 4 times the size of the
> physical memory to run. If so!? It must be really, really badly
> broken (hopefully not by design).

I never said KDE required 4 times core RAM. What i said was:
the rule of thumb for sizing swap is at least 3 times core RAM.

Michael Szengel used to not have enough swap, and it caused problems.
Then he increased swap, and, as far as i can understand, the problems
went away. Is this fact relevant ? Would this fact suggest that the
original swap allocation (which was less than twice core RAM) was not
enough, and that increasing swap to something very close to 3 times
RAM was beneficial ?

Interestingly enough, my Sun boxes at home have each 2GB RAM and 6GB
swap
(Solaris 8 and 9). Guess what ? They both swap, about ~200MB worth.
Guess
another what: a minimal KDE takes about 300MB on each (running only
KMail,
3 xterms' and xemacs, which i am not counting). And i am not doing Monte
Carlo simulations at home.

--Stefan

-----

> >
> > Rolf Sponsel wrote:
> >
> >>Best Stefan,
> >>
> >>I really don't want to argue with you, but
> >>your experiences are different to mine, and
> >>I cannot find any support for your "rule of
> >>thumbs" in the Solaris documentation either. :-(
> >>
> >>http://docs.sun.com/db/doc/817-2874/6migoiaaj?q=swap&a=view
> >>docs.sun.com: System Administration Guide: Basic Administration
> >>
> >>Have a look under the title "Planning for Swap Space".
> >>
> >>Best Regards / Rolf
> >>
> >>BTW, I'm running GNOME 2.2 on Solaris 7
> >>      on a SPARCstation 5 with 128 MB and
> >>      512 MB Disk Swap quite acceptable.
> >>    ( the factor 4 here :-) accidentally
> >>      corresponds to what you recommend
> >>      mainly because I need that much when
> >>      compiling H323 software ). -Not bad.
> >>
> >>Stefan Teleman wrote:
> >>
> >>>based on:
> >>>
> >>>1. experience
> >>>2. a tendency of mine to grant more weight to factual, observed
> >>>behavior, rather than to one or another particular online article.
> >>>3. another tendency of mine to accept the fact that OS's in general
> >>>tend to do whatever they want to do, and swap the way they want to
> >>>swap, regardless of what people think or hope they _should_ be doing.
> >>>4. when faced with a fairly trivial problem which has three possible
> >>>solutions:
> >>>      a) shrink KDE
> >>>      b) rewrite the SunOS swapper
> >>>      c) increase swap
> >>>
> >>>i try to choose the most practical and easily implemented solution (c).
> >>>
> >>>:-)
> >>>
> >>>--Stefan
> >>>
> >>>-----
> >>>
> >>>Rolf Sponsel wrote:
> >>>
> >>>
> >>>>Stefan,
> >>>>
> >>>>What do you base that "rule of thumb" on?
> >>>>
> >>>>This sounds to me, like an old SunOS myth, and
> >>>>is not in accordance with, e.g. this article.
> >>>>
> >>>>http://www.itworld.com/Comp/2377/UIR960401perf/
> >>>>
> >>>>Best Regards / Rolf
> >>>>
> >>>>Stefan Teleman wrote:
> >>>>
> >>>>
> >>>>>The rule of thumb for determining the minimal amount of swap space is:
> >>>>>
> >>>>>at least 3 times core RAM.
> >>>>>
> >>>>>That means, for a workstation with 640MB core RAM you need _AT LEAST_
> >>>>>1920MB swap. which you can probably safely round up to 2048MB.
> >>>>>
> >>>>>Running out of swap on 640MB core with 1GB swap is not surprising at
> >>>>>all.
> >>>>>
> >>>>>--Stefan
> >>>>>
> >>>>>-----
> >>>>>
> >>>>>On Monday, January 26, 2004, Michael Szengel wrote:
> >>>>>
> >>>>>[ ... snip ... ]
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>>For your reference:  my Sun Blade 100 has 640 MB RAM and had 1 GB swap. I
> >>>>>>had to extend the swap by 500 MB in order to survive the days without the
> >>>>>>error message you mentioned.
> >>>>>
> >>>>>
> >>>>--
> >>>>----
> >>>>------
> >>>>--------
> >>>>
> >>>>Rolf Sponsel
> >>>>
> >>>>___________________________________________e_n_d___o_f___m_e_s_s_a_g_e_
> >>>
> >>>
> >>--
> >>----
> >>------
> >>--------
> >>
> >>Rolf Sponsel
> >>
> >>___________________________________________e_n_d___o_f___m_e_s_s_a_g_e_
> >
> >
> 
> --
> ----
> ------
> --------
> 
> Rolf Sponsel
> 
> ___________________________________________e_n_d___o_f___m_e_s_s_a_g_e_

-- 
NOTICE: If received in error, please destroy and notify sender.  Sender
does not waive confidentiality or privilege, and use is prohibited.