SUMMARY: memory and swap

From: Grant Lowe <>
Date: Sat Mar 18 2006 - 17:33:08 EST
Hi Gurus.

First, thanks go to the following:

Anthony D'Atri
Atul Gore
Matthew Stier
Casper Dik
Crist Clark
Darren Dunham

Several said basically this, to take a look at these

# swap -s
# swap -l

The most complete answer I got was this, from Crist:

Swapping out idle processes even when RAM is not full
or low is a Good Thing. Swapping out takes time and
resources. You want RAM free in case there is a sudden

For example, your system seems to be using about 15.7
GB total. Say it was all in RAM leaving a mere 300 MB
free. Suddenly a new or existing process needs another
2 GB of RAM. You need to suddenly swap out
a bunch of stuff. Think how long it takes to write 2
GB to a HDD. That would kill performance. Instead,
when processes are idle, they get swapped out whether
you are short on RAM or not so you never run into
this problem. If the data doesn't need to be in RAM
(isn't currently being used), why have it there?

There are of course situations where this heuristic is
non-ideal, but for almost all cases, swapping out idle
memory whether low on RAM or not improves the overall
performance of the system.


Lastly, the original question:

I've got a java app that sometimes run at 99% usr.  I
see that from vmstat, top, and sar.  When java runs,
it uses about 2 or 3 gigs of RAM, but about 10 gigs of
swap.  How can I get to use more RAM and less swap? 
This is a V440 with 16GB RAM, running Solaris 9. 
sunmanagers mailing list
Received on Sat Mar 18 17:33:50 2006

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