Question

[Logan Shaw]

On Tue, 5 Sep 2006, Glenn Steen wrote:
> On 05/09/06, Ken A <ka at pacific.net> wrote:
>> Rob Poe wrote:

>> >             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.

> 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:-)

Side issue, but IMHO a big swap is a way to turn one kind of
negative consequences (running out of virtual memory) into
another kind (system getting ridiculously slow).  So it's a
value judgement whether it's worth having big swap or not.

> 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:-).

Speaking of which, memory issues are always confusing on modern
operating systems with virtual memory (and the Linux "vmstat"
documentation isn't much help), so is it safe to assume that
vmstat's "si" and "so" columns are 0, then nothing is being
read/written to swap space?  That would be a pretty good
(but not perfect) indicator of relatively pressure for memory.

By the way, tiny amount of swap used should mean a pretty high
probability of no swapping going on.  The converse isn't true
(you can have lots of stuff residing in swap but nothing going
back and forth between there and RAM), though.

   - Logan