[OpenSTA-devel] [ opensta-Bugs-696350 ] OpenSTA limit of 1664 vusers/users ?

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Bugs item #696350, was opened at 2003-03-02 23:18
Message generated for change (Comment added) made by faught
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Category: HTTP Replay
Group: Behavioral
Status: Open
Resolution: None
Priority: 5
Submitted By: Ranjit Shewale (jcrvs)
Assigned to: Daniel Sutcliffe (dansut)
Summary: OpenSTA limit of 1664 vusers/users ?

Initial Comment:
OpenSTA does not display and message when it 
reaches the user/vuser limit of 1664. 
As the test continues the vusers go on loading to a limit 
of 1664 and donot increase beyond that for the http or 
web scripts. 
This is observed on platform as Windows NT Server 4.0 
with SP6.
The marked observations (reported by perfmon) as the 
1664 user limit are as follows:-
1. Handle count for the TExecutor_htp.exe - it rises 
gradually as the test starts till it reaches the saturation 
point and then remains stable (drops to 0 when the test 
stops). Now the saturation point corresponds to the 
point where cpu utilization starts increasing and later 
reaches 100%.
2. Context switches of system are high in the region 
where the cpu utilization is 100%.
3. Exception dispatches per sec are high in the region 
where the cpu  utilization is 100%.
4. File Control Operations/sec are high in the region 
where the cpu  utilization is 100%

(My conculsion: 
This makes me conclude that the NT machine 'handle 
limit' is probably around 3734 or so and when opensta 
requests more handles to the system the system starts 
returning exceptions, hence the exceptions observed are 
high here as mentioned in point 3 above

The NT help for 'File Control Operations/sec' 
says 'operations usually include file system control 
requests or requests for information about device 
characteristics or status'. This could alos be one of the 
reasons for the problem. Something like opensta is 
internally making calls to get the status of cretain 
threads etc and results into pushing the server queue to 
higher value. This in turn increases the context switches 
amongst threads)

For other non-http scripts with huge delays as 10 
minutes or so, the OpenSTA is able to exceedd the user 
limit of 1664.

There is no documentation that mentions the above 
1664 vuser limit/bug.

The perfmon file is attached for reference. Unzip the file 
and open it using the NT4.0 perfom tool.

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Comment By: Danny Faught (faught)
Date: 2006-05-03 09:43

Message:
Logged In: YES 
user_id=576825

I'm copying this from bug 1480597 at Dan's request:

I'm seeing an easily reproducible crash with OpenSTA
1.4.3.20 on Windows XP Pro SP2.

1. In the Commander, create a test and add a task group
with any test script. I reproduced the crash using a
variety of scripts, including a skeleton script no with
executable statements at all.
2. Click the cell in the Start column and choose a
method for stopping the task group. The crash is
reproducible with any of the options - Manually, After
fixed time, and On Completion.
3. Set the number of virtual users for the task group
to 1666 or more.
4. Run the test. When it completes, I get the error
"TExecuter_HTP.exe has encountered a problem and needs
to close." Sometimes the error repeats when I dismiss
the error dialog, for a total of 6 times. 

The Commander seems to still be running fine, though
I'm not sure if the results are recorded correctly. The
Test Error Log shows an error for the location
"TestExecuter" - "General exception while running the
thread pool." This error also appears when I run with
1665 virtual users, though I don't reproduce the crash
in that case.

The workaround seems to be to not try to use more
virtual users than OpenSTA can handle (as per bug 
#696350). 

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Comment By: Danny Faught (faught)
Date: 2006-05-02 13:31

Message:
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Bug 1480597 is related to this one, but the result in that
case is a crash.

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Comment By: thefuzzball (thefuzzball)
Date: 2005-11-15 15:19

Message:
Logged In: YES 
user_id=1379239

Using opensta 1.4.3.20

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Comment By: thefuzzball (thefuzzball)
Date: 2005-11-15 15:16

Message:
Logged In: YES 
user_id=1379239

Replicated this on Windows Server 2003 standard edition. 
Dual 3.2 GHZ Xeon w/ 2G ram

CPU load hovered around 97% avg. for both processors.  It
crashed the box within seconds after the 1664 users were met.

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Comment By: Daniel Sutcliffe (dansut)
Date: 2003-04-29 21:05

Message:
Logged In: YES 
user_id=19748

More info can be added and read at:
http://portal.opensta.org/faq.php?topic=BugsMaxVu

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Comment By: Ranjit Shewale (jcrvs)
Date: 2003-03-02 23:22

Message:
Logged In: YES 
user_id=721091

Sorry forgot to attach the file

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