Question

[Glenn Steen]

On 06/09/06, Ken A <ka at pacific.net> wrote:
>
>
> Glenn Steen wrote:
> > On 05/09/06, Ken A <ka at pacific.net> wrote:
> >>
> >>
> >> Rob Poe wrote:
> >> >> I have a client with an older linux box running MailScanner and
> >> it's just being crushed ... with spam....
> >> >>
> >> >> It's a Celeron 2.0 ghz / 512mb ram / dual IDE disk
> >> >>
> >> >>  10:55:02  up 19:05,  1 user,  load average: 6.23, 4.56, 4.04
> >> >
> >> >> Seeing things like this:  Sep  5 10:56:12 mail MailScanner[25809]:
> >> Batch processed in 61.70 seconds
> >> >>
> >> >> I've tried 5, 3 and now 2 MS children.
> >> >>
> >> >
> >> >> What does 'free' report? Using swap? Increase MS children up to 4 or 5
> >> >> until they start using swap, or add ram if they are already swapping.
> >> >
> >> >             total       used       free     shared    buffers
> >> cached
> >> > Mem:        479644     447512      32132          0      93536
> >> 161792
> >> > -/+ buffers/cache:     192184     287460
> >> > Swap:      2112440       4356    2108084
> >>
> >> Looks like you are pushing it already at 2 children. More memory would
> >> help. You should be able to run 4 MS processes with a GB of ram.
> >
> > Ah, beg to differ, if but a tad...:-)
> >  There is quite a bit of free memory there (both really free and
> > "readily returnable":-), so that isn't likely "it". The total is a bit
> > off from 512 MiB, which indicate that the machine have some memory
> > snitched by a "share memory" VGA adapter (or similar)... Install the
> > cheapest real VGA card you can find and disable the share-memory
> > thing, if possible. And get some more real RAM, a big swap is just a
> > crutch:-)
>
> Our mailscanner processes are ~100mb each. So... did you used to try to
> squeeze and extra 10k out of your 386 dos machine, so you could run
> doom? :-)

It's all a question of relative sizes... On an ABC80 (Luxor computer,
based around the Z80 chip) saving 10 KiB would mean saving most of the
available memory;-):-)...
At a previous job (manufacturing industry) they actually had to do
stupid things like that, but not for doom, rather to get the
production 386:s to both have the homegrown production app and a
"network client" running at the same time. One can say I'm familiar
with the concept.

In this case you have more than 100 MiB available, which means that
_as it is set now_ it doesn't have an immediate memory problem. One MS
child more though, and things might hit the fan, at a disturbing
rate:-). Having another 32 MiB "locked" to some piece of **** onboard
VGA chip, in that context, isn't particularly good. Every bit that can
improve a somewhat resource-starved system....
But as with disks, RAM is cheap these days, so...:-)

> > But that's neither here nor there. The tiny amount of swap used
> > doesn't really tell much.... "vmstat 2" is the tool to look to first,
> > to see if you have any swap in/out activity (I'm guessing you'll not
> > see much in that department:-).
>
> good catch. It is hard to tell from the 'free' report above what is
> actually happening, and vmstat will show you that and more

Yes well, vmstats si/so is really the only info worth monitoring with
that particular tool, IMO.

> > The high load means you're either waiting for CPU or I/O. Good tools
> > to look at this (apart from what vmstat can tell you) are top, sar and
> > iostat (start with top and iostat, which will help you determine
> > what's up in the short term, and then move on to setting sar up....
> > that way you'll get some history to lean on in the future:).
>
> Another plus from adding some ram is that you can add a nameserver to
> the box to speed up rbl lookups and/or a rbldnsd to serve them locally.
>
Oh yes. A very good idea that.

-- 
-- Glenn
email: glenn < dot > steen < at > gmail < dot > com
work: glenn < dot > steen < at > ap1 < dot > se