[kde-solaris] ... people are running KDE3 on systems with as little as 64MB for daily use.

[Stefan Teleman]

Hi! :-)

My replies are inlined.

On Wednesday 28 January 2004 05:41, Rolf Sponsel wrote:
> Please bear with me ;-) this is *not* a flame.
> I'm just trying to understand this better.
>
>
> Obviously there is something that I
> haven't understood yet about Solaris.

There are many things i don't understand about Solaris either. :-)
>
>  From my understanding, for Solaris 2 (SPARC),
> the *available memory* is RAM + SWAP (which
> can be either on a separate partition, or
> a swap file on any ordinary partition).

Yes.

>
> Additionally, the '/tmp' file system (by
> default) is allocated from the space of
> available memory.

This is what i am not sure about. My understanding is that, on 
Solaris, if /tmp is not mounted on its separate disk partition, the 
kernel will create a TMPFS partition on /tmp when mounting swap, at 
boot time, and mount swap on it -- if this is not true, and i am 
being bogus, please say so. :-) With this configuration, this 
explains why, when rebooting Solaris, the files in /tmp are gone, and 
/tmp is re-created. Now, if, during normal usage/running of Solaris, 
some big files accumulate under /tmp (which is mounted as TMPFS) they 
will take space out of the swap partition, in fact. So, the system 
may have, initially, started out with plenty of virtual memory, but 
something (or somethings) got dumped or written to /tmp, or written 
to, /tmp, and now they are taking a lot of space from swap. So, all 
of a sudden there's a swap space problem when there didn't use to be 
one. Best way to avoid it, is to mount /tmp under its own personal 
disk partition, which is what Marco was suggesting the other day -- 
my Sun boxes, and many Sun boxes i've seen are configured this way.

>
> Now, if one has a set of applications that
> run fine on, let's say 128MB RAM (alt .5GB)
> and 384MB SWAP (alt 1.5GB); then I don't
> understand why that *same* set of applications
> with the configuration .5GB (alt 2GB) and
> 0MB SWAP (alt 0GB) should *not* run fine.

It could be the thing above. And it could also very well be that, the 
swapper makes decisions on how and when to swap based on the size of 
core RAM. One machine has little RAM, the swapper decides "well, 
there's probably going to be not a lot of swap, so i better behave".  
Another machine has a lot of RAM, the swapper decides "lots of RAM, 
i'm going to swap, to keep as much core free as possible". 

There's one other aspect: Linux seems to have very different swapping 
habits than Solaris. My experience has been that Linux tries to avoid 
swapping at all costs, whereas Solaris tries to keep as much free 
core as possible, and swaps significantly more than Linux.

--Stefan

------

>
>
> Best Regards / Rolf
>
>
> Ps. I could accept the "magic" fact that one
>      needs a swap of about 3 times RAM, but I
>      do not yet understan why. I'm sure it's
>      explained somewhere, but so far I haven't
>      managed to find that information/document.
>
> Stefan Teleman wrote:
> > The problems you are having are not related to RAM. They are
> > directly caused by the size of your swap partition, which is too
> > small. If you increase swap to at least 3 times core RAM, you
> > will no longer have these problems. I personally know of at least
> > one person happily running the same 3.1.4 binaries on an Ultra 5
> > with 256MB RAM, and with a correctly sized swap (which in this
> > particular case, is more than 3 times RAM).
> >
> > Comparing identical software's memory footprint between 2
> > different OS's running on different hardware architectures built
> > with different compilers is not relevant. Binaries at identical
> > software release numbers, from identical source code, will have
> > different sizes on different operating systems with different
> > compilers.
> >
> > I cannot confirm any of these miniature KDE sizes running on
> > Linux, and i have been running KDE on Linux (RedHat) since KDE
> > 2.2. Currently, i am running 3.1.4, with the binary build
> > downloaded from KDE, on RedHat 9, on a 1.2GHz P4 with 512MB
> > ThinkPad. It is configured with 1.5GB swap. With only KMail, 4
> > xterms and one Konsole running, i see a memory footprint of 420MB
> > in use, and 170MB swap in use, as reported by KSysguard (the swap
> > could very well be some other system stuff running in the
> > background).
> >
> > These sizes are consistent with what i see on the Solaris build
> > (it's actually less on Solaris, for the same exact apps), and
> > with what i have seen with KDE 3.0.* on Linux.
> >
> > I also do not remember KDE 2.2 using less than 350MB RAM on
> > Linux.
> >
> > Even with this resource footprint, this laptop performs very well
> > its additional duties of NFS and NIS server for my 2 Sun boxes at
> > home, and i am exporting an external USB drive with two 40GB
> > partitions. And i can also build additional KDE software from
> > source, with gcc, on this laptop, while it's doing its job.
> >
> > --Stefan
> >
> > ----
> >
> > On Tuesday 27 January 2004 12:16, michael.szengel at philips.com 
wrote:
> >>Since I am the guy who caused this discussion I would like to
> >> share my personal (over 10 years) experience with memory usage
> >> of Sun systems and finally ask for a reason.
> >>I never experienced memory shortages on our Sun systems running
> >>only a desktop since the days of SPARCstation 1 with 16 MB RAM
> >> and about 45 MB swap (not counting the cases when sombody was
> >> trying to start a whole chip simulation on his desktop mashine
> >> ;-). For 4 years, my colleagues work on Ultra10 / Sun BLade 100
> >> with 512 MB RAM and 1 GB swap ... and never problems with
> >> memory.  Some of them open up to 10 desktops with dozens of
> >> terminals, xemacs and other stuff. They criticized the Xserver
> >> because they can not open more than about 80 windows at a time
> >> due to a resource limitation inside of X but they never run into
> >> memory problems under KDE2 (gcc version).
> >>Now I installed KDE3 from Stefan on my mashine to try it out and
> >>only the KDE3 desktop with some terminals and other desktop tools
> >>(not talking about MATLAB or a VHDL simulator, which is quit
> >> common to use for smaller tasks on our desktops here as well)
> >> let crash my Sun due to a shortage of memory !!!!
> >>
> >>I do not have a explanation for the tremendious increase in RAM
> >>usage. And this has been  the main reason for me not to start
> >> with a rollout of the otherwise stable KDE3 release from Stefan
> >> because I will have to repartition / reinstall all my Sun
> >> desktops.
> >>
> >>Any root cause explanation of this effect is very welcome and I
> >>would be very happy if the myth about KDE3 on 64MB RAM becomes a
> >>reality ;-)
> >>
> >>Just my experience, not a flame.
> >>
> >>Michael

-- 
Stefan Teleman          'Nobody Expects the Spanish Inquisition'
steleman at nyc.rr.com                          -Monty Python