Thrashing WITHOUT swap.

Thrashing WITHOUT swap.

[Maciej Zenczykowski]

Hi All,

I have a queer problem.

This is happening on a freshly installed RH7.1 notebook.
Celeron 400 + 64 mb ram, kernel as shipped (2.4.2-2, have not even
recompiled it yet).  I have a 140 mb swap partition set up but at the time
this happened it was OFF.  I was (still am) running X + twm + two xterms
with ssh + netscape (this is probably the cause of the entire problem).
I had a single netscape window open with a mid-graphic intensive screen.
The system started thrashing...  Now my question is how can it be
thrashing with swap explicitly turned off? [oh just to make stuff even
funnier netscape is at nice -19 (i.e. lower priority)]

top gives me:
mem: 62144k av, 61180k used, 956k free, 0k shrd, 76 buff, 2636 cached
swap: 0k av, 0k used, 0k free [as expected]

cpu states: 0% user, 99.9% system, 0.0% nice, 0.0% idle

process list:
99 % cpu, CTIME: 29:24 kswap...

all other processes have decent time and cpu usage lists
even X has a CTIME of only 11 minutes
[well init has 260:10 but that is normal..., system has been up 3 days]

So my basic question is what can I do to fix this?

I expect (only explanation I can find) that the problem is Netscape
mmaping files.

Oh, and Netscape is not dead it is just very slow [like the entire system,
I can watch top refresh the screen in line by line mode...]

Any help would be appreciated...

Maciej Zenczykowski
<maze@druid.if.uj.edu.pl>

Re: Thrashing WITHOUT swap.

[Jonathan Morton]

>Now my question is how can it be
>thrashing with swap explicitly turned off?

Easy.  All applications are themselves swap space - the binary is 
merely memory-mapped onto the executable file.  When the system gets 
low on memory, the only thing it can do is purge some binary pages, 
and then repeatedly page them back in from the original executable 
file.

If you added a little bit of swap, it would be able to page out some 
idle data rather than binaries, and would probably avoid thrashing.
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Re: Thrashing WITHOUT swap.

[Alan Cox]

> recompiled it yet).  I have a 140 mb swap partition set up but at the time
> this happened it was OFF.  I was (still am) running X + twm + two xterms
> 
> top gives me:
> mem: 62144k av, 61180k used, 956k free, 0k shrd, 76 buff, 2636 cached
> swap: 0k av, 0k used, 0k free [as expected]

Not as expected - 0k used 0k free - you have no swap

Alan

Re: Thrashing WITHOUT swap.

[Xavier Bestel]

On 24 Jun 2001 22:36:25 +0100, Alan Cox wrote:
> > recompiled it yet).  I have a 140 mb swap partition set up but at the time
> > this happened it was OFF.  I was (still am) running X + twm + two xterms
> > 
> > top gives me:
> > mem: 62144k av, 61180k used, 956k free, 0k shrd, 76 buff, 2636 cached
> > swap: 0k av, 0k used, 0k free [as expected]
> 
> Not as expected - 0k used 0k free - you have no swap

That's what he said. *WITHOUT* swap.

Xav

Re: Thrashing WITHOUT swap.

[Mike Galbraith]

On 25 Jun 2001, Xavier Bestel wrote:

> On 24 Jun 2001 22:36:25 +0100, Alan Cox wrote:
> > > recompiled it yet).  I have a 140 mb swap partition set up but at the time
> > > this happened it was OFF.  I was (still am) running X + twm + two xterms
> > >
> > > top gives me:
> > > mem: 62144k av, 61180k used, 956k free, 0k shrd, 76 buff, 2636 cached
> > > swap: 0k av, 0k used, 0k free [as expected]
> >
> > Not as expected - 0k used 0k free - you have no swap
>
> That's what he said. *WITHOUT* swap.

:)) yeah, exactly what Alan said.

	-Mike

Re: Thrashing WITHOUT swap.

[Helge Hafting]

Maciej Zenczykowski wrote:
> Now my question is how can it be
> thrashing with swap explicitly turned off? 

Easy.  Linux throws executables out from memory because they _can_
be fetched again from disk.  Yes - this definitely gives trashing
if you loose almost all your executables this way.

> [oh just to make stuff even
> funnier netscape is at nice -19 (i.e. lower priority)]

That makes no difference.  nice'ing netscape means it use
less _cpu when other things want cpu_, it can still over-spend memory!

> top gives me:
> mem: 62144k av, 61180k used, 956k free, 0k shrd, 76 buff, 2636 cached
> swap: 0k av, 0k used, 0k free [as expected]

File i/o becomes a pain with so few buffers and cache pages left, and
then your file i/o and the executable fetching competes for
the disk.  No wonder it got slow, and laptop disks aren't usually
that fast either...
 
> So my basic question is what can I do to fix this?
Looks like you were 3M away from running completely out of memory.
Turn on that swap partition you mentioned, your machine will degrade
much more gracefully.  It'll keep more cache around and be able
to get rid of unused data instead of just dropping executables.
Some of the code is used a lot after all.

If it still is too slow - add RAM or run fewer/smaller apps.
Opera is a low-memory alternative to netscape.  Avoiding
gnome/kde apps when plain X apps are available is also a good idea
when you're short on memory.  Using low resolution and low-color
modes might help a little if you do lot of graphics.  But then
you might not want that.

Helge Hafting

[OT] Re: Thrashing WITHOUT swap.

[Daniel Phillips]

On Monday 25 June 2001 11:21, Helge Hafting wrote:
> If it still is too slow - add RAM or run fewer/smaller apps.
> Opera is a low-memory alternative to netscape.  Avoiding
> gnome/kde apps when plain X apps are available is also a good idea
> when you're short on memory.  Using low resolution and low-color
> modes might help a little if you do lot of graphics.  But then
> you might not want that.

Further to that, I followed Alan's lead and installed xfce.  My laptop, which 
was really suffering under Gnome with 64 meg (much more so under KDE) is 
suddenly light on its feet.  Not to mention that it built from source in 
under 10 minutes and installed with zero 'interesting problems'.

After another year of optimizing the kernel to handle bloatware better, and 
at the same time encouraging the 'big desktop' side of Linux to follow the 
lead of these lightweight alternatives[1] we will be looking pretty good.

--
Daniel

[1] by voting with our feet

Re: [OT] Re: Thrashing WITHOUT swap.

[Colonel]

In clouddancer.list.kernel, you wrote:
>
>Further to that, I followed Alan's lead and installed xfce.  My laptop, which 
>was really suffering under Gnome with 64 meg (much more so under KDE) is 
>suddenly light on its feet.  Not to mention that it built from source in 
>under 10 minutes and installed with zero 'interesting problems'.
>
>After another year of optimizing the kernel to handle bloatware better, and 
>at the same time encouraging the 'big desktop' side of Linux to follow the 
>lead of these lightweight alternatives[1] we will be looking pretty good.


Had you tried fvwm-1.24r (the original) ?  It was designed long ago to
be lean and fast on the desktop.  I know it whips KDE.

Re: [OT] Re: Thrashing WITHOUT swap.

[Daniel Phillips]

On Monday 25 June 2001 18:16, Colonel wrote:
> In clouddancer.list.kernel, you wrote:
> >Further to that, I followed Alan's lead and installed xfce.  My laptop,
> > which was really suffering under Gnome with 64 meg (much more so under
> > KDE) is suddenly light on its feet.  Not to mention that it built from
> > source in under 10 minutes and installed with zero 'interesting
> > problems'.
> >
> >After another year of optimizing the kernel to handle bloatware better,
> > and at the same time encouraging the 'big desktop' side of Linux to
> > follow the lead of these lightweight alternatives[1] we will be looking
> > pretty good.
>
> Had you tried fvwm-1.24r (the original) ?  It was designed long ago to
> be lean and fast on the desktop.  I know it whips KDE.

Yes, I did.  It's even faster than xfce but there's one problem: it just 
isn't very much like a modern desktop.  xfce is, to a surprising degree, like 
a modern desktop.  It's roughly equivalent to W95 I'd say - more 
sophisticated in some areas, less in others.  Oh, did I mention I haven't run 
into a bug yet?  It's true.

--
Daniel

Re: [OT] Re: Thrashing WITHOUT swap.

[john slee]

On Mon, Jun 25, 2001 at 06:32:16PM +0200, Daniel Phillips wrote:
> On Monday 25 June 2001 18:16, Colonel wrote:
> > Had you tried fvwm-1.24r (the original) ?  It was designed long ago to
> > be lean and fast on the desktop.  I know it whips KDE.
> 
> Yes, I did.  It's even faster than xfce but there's one problem: it just
> isn't very much like a modern desktop.  xfce is, to a surprising degree, like
> a modern desktop.  It's roughly equivalent to W95 I'd say - more
> sophisticated in some areas, less in others.  Oh, did I mention I haven't run
> into a bug yet?  It's true.

firstly, i better have at least one paragraph related to the kernel ;)
2.4 is a *much* better desktop than 2.2 for me.  make -j32 bzImage and
other large amounts of processes/io don't destroy the interactivity of
my X session anymore.

(wearing asbestos suit)

i have run, as full-time desktops, kde-1.x, enlightenment, windowmaker
and fvwm-* on 10baseT switched networks with Tektronix XP400 terminals
hosted on linux (and of course on xfree86-based normal linux desktops)

in both cases the better and "more interactive" window manager was not
fvwm or wmaker.  sure, E can be a pig with the right theme, but with a
nice lightweight theme it is great. E certainly seems lots better over
ethernet than the other two...

kde 1.x of course was absolutely ghastly over a network (gnome not too 
prominent in those days, so i didn't get a chance to try it)

lately i have been trying to make kde2 run smooth like my E setup, but
there are some niggles, and i wouldn't bother if i had less than 256mb
ram.

j.

-- 
"Bobby, jiggle Grandpa's rat so it looks alive, please" -- gary larson

Re: Thrashing WITHOUT swap.

[Ookhoi]

Hi Maciej Zenczykowski,

> This is happening on a freshly installed RH7.1 notebook.
> Celeron 400 + 64 mb ram, kernel as shipped (2.4.2-2, have not even
> recompiled it yet).  I have a 140 mb swap partition set up but at the time
> this happened it was OFF.  I was (still am) running X + twm + two xterms
> with ssh + netscape (this is probably the cause of the entire problem).
> I had a single netscape window open with a mid-graphic intensive screen.
> The system started thrashing...  Now my question is how can it be
> thrashing with swap explicitly turned off? [oh just to make stuff even
> funnier netscape is at nice -19 (i.e. lower priority)]

nice -19 means high priority doesn't it? It is not nice towards other
processes.

	Ookhoi