Onmode -F
Asked whether running 'onmode -F' (free unused shared-memory segments) frequently causes performance problems, on IDS 7.31.UD8 / AIX 5.2, 4 CPUs, 32-bit 2GB instances. Replies: in principle it's harmless, but bugs have been reported where -F interferes with running threads causing assert failures/crashes, so run it only off-peak or when free virtual memory blocks drop low. Also, freeing segments that applications soon need again just incurs re-allocation overhead; better to tune initial/additional segment sizes to keep segment count low and set a memory ceiling. From IDS 9.x on, memory is drained automatically so -F is generally unnecessary (unless DONTDRAINPOOLS is set). Advice rather than a single fix.
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Hi Guys,
Are there any perf issues related to running onmode -F too frequently. Your
answers are greatly appreciated!
Thanks
jp
Version of IDS? OS? CPUs and memory?
Bob Roussey
Robert.Roussey@SpiritAir.com
-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
jpierrot@ch....
Sent: Wednesday, March 22, 2006 11:00 AM
To: ids@iiug.org
Subject: Onmode -F [6530]
Hi Guys,
Are there any perf issues related to running onmode -F too frequently.
Your
answers are greatly appreciated!
Thanks
jp
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version : IDS7.31.UD8
OS : AIX 5.2
CPU's : 4
Mem : 8GB RAM
but can only allocate/use 2gbs per instance due to 32 bits software
limitations
jp
"Robert Rous...."
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RE: Onmode -F [6531]
03/22/2006 11:25
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Please respond to
ids@iiug.org
Version of IDS? OS? CPUs and memory?
Bob Roussey
Robert.Roussey@SpiritAir.com
-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
jpierrot@ch....
Sent: Wednesday, March 22, 2006 11:00 AM
To: ids@iiug.org
Subject: Onmode -F [6530]
Hi Guys,
Are there any perf issues related to running onmode -F too frequently.
Your
answers are greatly appreciated!
Thanks
jp
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Not sure ... we run ours at 6:00 AM daily because it seemed like the thing
to do at the time.
John Caron
USBC-MA
Worcester 508-770-8957
Boston 617-565-6175
Cell 508-509-6574
"Robert Rous...."
<Robert.Roussey@S
piritAir.com> To
Sent by: ids@iiug.org
ids-bounces@iiug. cc
org
Subject
RE: Onmode -F [6531]
03/22/2006 11:25
AM
Please respond to
ids@iiug.org
Version of IDS? OS? CPUs and memory?
Bob Roussey
Robert.Roussey@SpiritAir.com
-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
jpierrot@ch....
Sent: Wednesday, March 22, 2006 11:00 AM
To: ids@iiug.org
Subject: Onmode -F [6530]
Hi Guys,
Are there any perf issues related to running onmode -F too frequently.
Your
answers are greatly appreciated!
Thanks
jp
************************************************************************
*******
Forum Note: Use "Reply" to post a response in the discussion forum.
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jpierrot@ch.... wrote
> Hi Guys,
> Are there any perf issues related to running onmode -F too
> frequently. Your
> answers are greatly appreciated!
>
Yes No - there shouldn't , but
Experience shows, that very now and then product defects (aka bugs) are
reported
that cause inconvienece (aka assert Failures and crashes) when onmode
-F
interferes with running threas in the IDS server.
So , from my experience, I'd run it only at off-peak times , and or only
when number
of freeblks in Virtual shared memory goes down beyond some limit.
In IDS 9.x and higher, 'onmode -F' shouldn't be necessary, unless you
have set DONTDRAINPOOLS
in IDS environment. In these versions, memory is returned from session
pools to the pool
of free memory blocks in virtual shared memory automatically.
jpierrot@ch.... wrote:
> Hi Guys,
> Are there any perf issues related to running onmode -F too frequently. Your
> answers are greatly appreciated!
There are overheads associated with allocating a new segment. If your
applications are using that memory regularly, then it is not a good idea to
free it up when they are not looking, only to have it re-allocated again
when they need it.
As someone said, application issues can sometime cause extra segments to be
allocated as a one-off situation, so it might be applicable to remove them
once the crisis is over. I have never had to resort to performing that via
crontab though.
Also, if your applications are using several segments regularly, then you
should consider tuning the initial and additional segment sizes to minimise
the total number of segments. Allocating a large number (more than 2 on
some systems) of segments can also cause performance problems.
If your system really can't stand the occasional application crisis, then
set the maximum size to limit memory allocation. This will cause errors at
the application and possibly cause it to fail, but that is possibly better
than bringing the entire system to its knees.
Cheers,
--
Mark.
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