From: Willeat, Todd (TWilleat@MHP.SMHS.COM)
Date: Tue Aug 06 2002 - 12:03:43 EDT
Hi all,
I have a question for all of the performance tuners out there. I've been
testing a program called SarCheck and it has suggested that the schedtune -m
setting (default = 2) may be too low. IBM's docs say:
The system default of m=2 ensures that the kernel, all pinned processes, and
two user processes will always be in the set of processes competing for RAM.
While m=2 is appropriate for a desktop, single-user configuration, it is
frequently too small for larger, multiuser, or server configurations with
large amounts of RAM.
If the system you are installing is larger than 32 MB, but less than 128 MB,
and is expected to support more than five active users at one time, consider
raising the minimum level of multiprogramming of the VMM memory-load-control
mechanism.
As an example, if your conservative estimate is that four of your most
memory-intensive applications should be able to run simultaneously, leaving
at least 16 MB for the operating system and 25 percent of real memory for
file pages, you could increase the minimum multiprogramming level from the
default of 2 to 4 with the following command:
# /usr/samples/kernel/schedtune -m 4
On these systems, setting m to 4 or 6 may result in the best performance.
Lower values of m, while allowed, mean that at times as few as one user
process may be active.
For our app, each user runs a separate process that uses around 2MB of
memory and we have a maximum of 350 of these processes running concurrently.
We currently have 14.5GB of RAM in the box.
My question - Would anyone recommend changing this setting, and if so, what
value would be suggested?
Thanks for any input.
_______________________________________
/ Todd A. Willeat \
| UNIX Administrator |
| Mercy Health Plans |
| 425 South Woods Mill Road |
_ | Chesterfield, Missouri 63017-3492 | _
/ )| (314) 214-2329 / (314) 214-8202 (fax) |( \
/ / | twilleat@mhp.mercy.net | \ \
_( (_ | http://www.mercyhealthplans.com/ | _) )_
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