SUMMARY for performance problem on a Sparc20

From: Richard Savage (
Date: Wed May 01 1996 - 14:50:04 CDT


Here is my summary for the problem I submit earlier this week.
 will and I did use a combinaison of some of the tips that you give me

First I got rid of some process in my crontab that were taking a lot of CPU's
and memory and didn't need to be ran as often...

I'm also in the process of checking carefully my performance with sar and ProCtool

And I'm also planning to upgrade to 2.5 pretty soon now..

Any other comments you might have are still welcome....

Thank you again!!


> For the last two week, I had to reboot this server two or three time du to
> the fact that I was not able to start a telnet session on it or even get a
> console access...
> I talk with Sun about that and we came to the conclusion that the problem
> was one of those:
> - I'm running out of processes
> - I'm running out of swap space
> My swap space is set to 256Mb. so we concentrate on the processes first.
> The guy at Sun said that I need to augment my max_users to 64, since it is
> to 16 by default. At first it make sense, but after reading in Adrian
> Cockcroft book that in Solaris 2.4 and up this value is set dynamically
> depanding of your amount of memeory, I began to think back...

Here is the answers I got:

From: "Matthew D. Lammers" <>

Whoa! You need to have MORE swap...swap space must be larger than
your physical memory, especially running X.

A GOOD rule is double your physical memory, and make that
amount your swap partition. In your case, 512MB is the
least amount of swap/paging space you need. Also, I
recommend breaking it up across filesystems to improve

It used to be ( many years back ) that we made four times the
physical memory for swap... Nearly 1 GB in your case...

As for your max_users variable in your kernel, I doubt this
to be a problem, as it's more of a suggestion or starting
point. However, when running X, you should configure one 'user'
for each window and login...64 is a good start.

If you need help re-sizing your swap, consult the Sun DOCs, as
this should ONLY be done with Suninstall or by an experienced
system admin...

From: (Ron Spillane)

Maybe what the Sun guy was trying to say was that you may need to increase
the number of telnet sessions aloud on your system. By default this is 48
sessions and can be increased or decreased in /etc/system by setting the
variables pt_cnt & npty. ie

        set pt_cnt=100
        set npty=100
Also you are correct about maxusers, it will be automatically set depending on
the amount of memory in your machine. I have checked this several times now on
systems running Solaris 2.3 and up and it consistently sets the value to 4 less
than amount of memory in the system. In your case it would be set to 252 and
should not changed unless you want to increase the maxusers variable.

From: Alex Finkel <>

Get a copy of Proctool from

You'll be able to gather information on processes, swap, IO, among other things.
Proctool will also let you monitor how your CPUs are being utilized by the

Similarly, get the SE 2.4 toolkit also from It lets you
gather some of the same information, but in a different way and lets you
adjust the rules it follows to make determinations.

From: Steve Phelps <>


        vmstat 1


        netsat -i 1

In two different windows and leave them running. When the problem occurs
check to see
if the CPU is spending most of its time in System mode (from vmstat). Check
to see
what network load is like at the time.

If System is spending lots of time in system mode then I reckon it could be
of a bug in Solaris 2.4 to do with the "discard" service. Run

        /usr/ucb/ps -aux | egrep -i discard

(Its important to use the ucb version). And see if there are any discard
processes running.
If there are then upgrade to Solaris 2.5.

From: Simon-Bernard Drolet <>

I could suggest you to really think about upgrading to 2.5. It's a lot more
efficient in memory management and you will have a performance gain of about
25 to 30%. Also, Solaris 2.5 use less memory and swap space.

In the book "Automating Solaris Installations", they giving you simple rules
to follow to define the amount of swap space you need.

In your case, since you have 256Mb of RAM, you don't need more than 128Mb of
swap. (page 99 in the book).


Setting max_users won't hurt.
Do you have sufficient ptys? Default is 48(?). Do you have more than 48
telnets at a time on your system?
in /etc/system
        set npty=128
        set pt_cnt=128
will set the number of 4.x pseudo-ttys (npty) and 5.x pseudo-ttys (ps_cnt).

Again, other than a small increase in kernel size, increasing max_users and
pseudo-ttys should have no negative effect.

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