[Beowulf] SWAP management

Lombard, David N david.n.lombard at intel.com
Fri Dec 12 09:51:51 EST 2003


From: Robert G. Brown; Sent: Friday, December 12, 2003 4:25 AM
> On Thu, 11 Dec 2003, Mark Hahn wrote:
> 
> > > It seems that my Linux OS [RH 7.3 basically, in some cases SuSE
8.2]
> > > tries to avoid that the percentage of memory used by a single
process
> > > becomes higher than 60-70 %.
> >
> > I don't believe there is any such heuristic.  it wouldn't have
anything
> to do
> > with the distribution, of course, only with the kernel.
> 
> To add to Mark's comment, it is not exactly easy to see what's going
on
> with a system's memory usage.  Using top and/or vmstat for starters --
> vmstat 5 will let you differentiate "swap" events from other paging
and
> disk activity (possibly associated with applications) while letting
you
> see memory consumption in real time.  top will give you a lovely
picture
> of the active process space that auto-updates ever (interval) seconds.
> If you enter M, it will toggle into a mode where the list is sorted by
> memory consumption instead of run queue (which I find often misses
> problems, or rather flashes them up only rarely).  You can then look
at
> Size (full virtual memory allocation of process) and RSS (space the
> process is actually using in memory at the time) while looking at
total
> memory and swap usage in the header.

I find that atop is a valuable tool to see what going on in a system,
much better than standard top.

Atop doesn't display inactive processes, so your display isn't clutter
with processes you don't care about, regardless of your sort; atop also
shows the growth of both virtual and resident memory.  In addition, atop
also gives a very good look at the system, including cpu, memory, disk,
and network.

One final Good Thing, atop can keep raw data in files that you can
"replay" later, allowing you to see a time-history of activity on the
node.

Take a look at ftp://ftp.atcomputing.nl/pub/tools/linux/

-- 
David N. Lombard

My comments represent my opinions, not those of Intel.

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