also would be helpful to gather performance management info and read the
tuning characteristics of your iSeries
http://www.redbooks.ibm.com/redpapers/pdfs/redp4026.pdf
HTH,
Martin-
----- Original Message -----
From: "Dov Rosenberg" <[EMAIL PROTECTED]>
To: "Tomcat Users List" <users@tomcat.apache.org>; "Martin Gainty"
<[EMAIL PROTECTED]>
Sent: Thursday, December 15, 2005 11:29 PM
Subject: Re: Performance degradation under load
While you are running how many database connections does your database
report having open? You might want to use the tomcat manager status app to
see how many threads you are using, how many sessions are being created,
etc. Lots of sessions can eat up memory as well if they are not being
killed
off quickly enough. If you have lots of threads coming in, make sure to
set
your maxThreads and associated parameters to handle the load. Also check
your queue depth, once the queue fills up no more requests are going to
come
thru.
Is your database reporting any core dumps, or alerts, or deadlocks?
On 12/15/05 11:01 PM, "Peter Lin" <[EMAIL PROTECTED]> wrote:
under normal conditions, a single webserver shouldn't have several
thousand
DB connections. that seems a bit odd to me.
peter lin
On 12/15/05, Martin Gainty <[EMAIL PROTECTED]> wrote:
Marc-
what types of Coyote Point Equalizers are you using?
What does the Doc say about configuring the CPE for 30-40 consecutive
users?
Martin-
----- Original Message -----
From: "Marc Richards" <[EMAIL PROTECTED]>
To: "Tomcat Users List" <users@tomcat.apache.org>
Sent: Thursday, December 15, 2005 7:57 PM
Subject: Performance degradation under load
I have a performance issue that I'm having trouble
with - perhaps somebody has seen this sort of thing
before and can help me out.
Problem:
Under no load my page responses average about 1.2
seconds (according to jmeter tests), which is pretty
good considering the heavy jdbc useage of my
applications. However, once I begin to ramp up the
load to 30 or 40 consecutive users the performance
quickly degrades down to about 4 seconds average
response time. While this takes place, the machines
are only showing about 5% cpu utilization and have
3.5gb of memory freely available. Network resources
also appear to be free. So I definitely don't have a
hardware issue, especially considering that there are
two balanced machines and neither are showing more
than 5% busy. I seem to have a bottle neck somewhere
in the system, but am unsure how to track it down.
Setup background:
This is a new setup that's not in production yet. I'm
running Apache 2.05x and Tomcat 5.5x using mod_jk.
Apache and Tomcat reside together on both machines
(Win 2003), so there should be virtually no latency
between them. The machines are balanced on the front
end by Coyote Point Equalizers.
Tomcat is handling connection pooling to our iSeries
database server (db2, jdbc), but I'm not sure it's
working correctly because when I do netstat I see
several thousand db connections sitting at TIME_WAIT
(presumably abandoned and waiting to be cleaned up by
the pool manager). This could be one of my problems,
but I don't think it's the whole problem and I don't
know how to verify. The call to the pool manager is
actually coming from the Spring Framework, which
possibly has a bug in it, but I suspect instead that
Tomcat is not returning the connections to the pool
(unless I'm interpreting the existance of so many
connections entirely wrong to begin with).
I'm also using Tomcat to persist my sessions
occasionally (every 2 minutes) to the same iSeries.
I see several possible bottle neck points; the http
forward from the load balancer to the server machine
(very unlikely), the tcp communication between Tomcat
and Apache (maybe), the jdbc connections to the
iSeries (this is my top suspect at the moment) or some
sort of db collusion occuring on the sessions
persistance table.
The big question: Anybody know a slick way to find
out what it is?
Thanks,
-marc
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