How to tell when a job is swapping?

Rocky McGaugh rmcgaugh at
Tue Feb 19 06:49:06 PST 2002

Jeff Layton wrote:

> Good morning,
>    For a while now I've been checking if a job is swapping
> on our clusters using bWatch. The nodes are dual CPU
> boxes and we run two MPI processes per node. I usually
> look at the load on the nodes to see if it is above 3.0
> (sometimes our code will peak out at about 2.3) and I
> look at the free swap space number (bWatch just cats the
> /proc/meminfo file).
>    I usually assume that if the free swap space falls below
> the maximum and load starts climbing that the node is
> swapping. However, when I talk to the user, he states that
> the code is running fine and the timing numbers are where
> they should be. So, I'm obviously interpreting something
> incorrectly (unless the job is really swapping but for some
> reason performance is unaffected).
>    Does someone give me a could way to check if a job
> is swapping? Maybe a URL?
> TIA,
> Jeff

Check out the PCP stuff from SGI. 

It will pull out:, swap.out, swap.pagesin, swap.pagesout,, swap.length, swap.used

It is also possible to compile the app against their tracing lib,
and get alot of info about the app itsself.

Rocky McGaugh
Atipa Technologies
rocky at
rmcgaugh at
1-785-841-9513 x3110
perl -e 'print unpack(u, ".=W=W+F%T:7\!A+F-O;0H`");'

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