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From "Robert Harper" <rob...@iat-cti.com>
Subject RE: Response time banding
Date Wed, 26 Jul 2006 20:47:00 GMT
One thing to consider is that the times may not be totally in synch. Some
threads pending a write to the log might get interrupted while another
thread runs. You may see log entries out of order. I have seen this myself
and have added System.out.flush() to my logger. It helps but still does not
ensure exact order. Make sure you go over the time stamps carefully before
you pass too much judgment.

Robert S. Harper
Information Access Technology, Inc.

-----Original Message-----
From: Leon Rosenberg [mailto:rosenberg.leon@googlemail.com] 
Sent: Wednesday, July 26, 2006 2:35 PM
To: Tomcat Users List
Subject: Re: Response time banding

I would measure at all layers during the request processing to
determine whether irregularities occur somewhere.

Leon

P.S. "the response times as measured by the access log" - don't you
have the proper tools for that? JMeter?

On 7/26/06, Edward Hibbert <Edward.Hibbert@dataconnection.com> wrote:
> Odd one, this.  I'm posting looking for off the wall suggestions.
> Though not too off the wall, please.
>
> We have an application running under Tomcat.  If we analyse the response
> times as measured by the access log, then we see that for the same GET
> operation there is a distribution of response times.  Well, you'd expect
> that.
>
> But while the bulk of response times are below about 0.25 seconds (in
> most cases considerably below), there is a banding effect where we get a
> cluster of response times around 2 seconds, and another cluster around 5
> seconds, with little or no values in between.
>
> We've looked at garbage collection as the most likely source of this,
> and ruled it out.  Has anyone seen anything similar, or got any bright
> ideas?
>
> Regards,
>
> Edward.
>
>

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