RE: Any clue on this, please? Uploading large files - out of memory

[Jeff Tulley <JT...@novell.com>]

Or, configuration.  Consider what I ran into the last few weeks.  We
were doing very high load testing of Tomcat and getting the dreaded
OutOfMemory error simply hitting the Tomcat examples.  I immediately
thought this to be bug as well.  Well, after using OptimizeIt on the
code, I found out that the culprit is that we were creating so many
sessions that we used up all of the memory before we hit the session
timeout.  This is a tuning problem, not a bug.  I could
1) Throw more memory at Tomcat (we had -Xmx256m)
2) Decrease the session timeout.  The default is good in most cases of
not-so-extreme traffic
3) Ponder on whether load testing 500-600 req/s, with each request
being a completely new session is a valid test scenario.  (Sometime it
is:  Think getting slash-dotted)

I also think that a lot of the more bizarre OOM errors being reported
on the user list currently, when reloading contexts for instance, have
to do with the newer GC model of new/old/permanent generation divisions
- the permanent generation is filling even though old and new have room
to spare.  This is also tuning.  (Well, the user did say that Sun is
doing a "fix" for that, so I guess it could be either)

That all said, OptimizeIt is well worth the money spent.  It vastly
decreased the amount of time spent tracking down my OOM error.  (After 3
or so days of staring at heap dumps, we just got OptimizeIt, and found
the problem almost immediately).

>On Wed, 3 Dec 2003, Adam Fisk wrote:
>
>> I've heard mention on this list many times of these
OutOfMemoryErrors
>> not being bugs.  I work on a Java app that experiences very high
network
>> traffic load, however, and it's been my experience that
>> OutOfMemoryErrors are, in fact, always bugs regardless of how
tempting
>> it is to chalk it up to something else.
>>
>> What makes everyone so certain it's not a bug or multiple bugs?
Since
>> you don't get stack traces and at best can pin down the thread name
for
>> OutOfMemoryErrors, they take a lot of time to track down.  In my
>> experience, though, they tend to result from an unaccounted for
>> degenerate request coming that causes the code to, well, consume
all
the
>> available memory (i.e., a bug).
>>
>> -Adam
>>
>>
>> Shapira, Yoav wrote:
>>
>> > Howdy,
>> > This belongs on the user, not dev, list.  It's most likely a
simple
>> > issue (not a bug) with you not allocating enough memory to the
JVM.
>> > Please pursue this issue on the user list.
>> >
>> > Yoav Shapira
>> > Millennium ChemInformatics


Jeff Tulley  (jtulley@novell.com)
(801)861-5322
Novell, Inc., The Leading Provider of Net Business Solutions
http://www.novell.com

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