Re: Is it Normal for Tomcat 8 to Use 20-80% More Memory Than Tomcat 6?

[Mark Thomas <ma...@apache.org>]

On 28/12/17 10:06, Olaf Kock wrote:
> 
> On 27.12.2017 23:16, Eric Robinson wrote:
>>> I mean A is java8 and tomcat8.. so make a C that is tomcat6 and java8
>> I don't think so. This is a requirement of the software company whose
>> application solution we use. They are requiring us to move to tomcat 8
>> with jdk 1.8. If we try to mix tomcat8 with jdk 1.6, supposedly we
>> would have problems. I guess all this is being driven by the need to
>> switch to TLS 1.2. I'm not sure if that would be a function of tomcat
>> or java.
> As you were looking for the reason of the increased footprint, this
> would help you tremendously to get to the root cause, even if you don't
> intend to use it in production. Assume that a similar behavior already
> appears when you run tomcat6 with Java8 - in this case there might be
> little reason to continue to dig in tomcat, and assume that it's the
> Java implementation that caused your increased footprint.
> 
> Tomcat 8 with Java 6 won't work (apart from the outdated implementation)
> as it requires at least Java7 (which is also outdated).
> 
> And then there's yet another aspect: The memory footprint increased way
> below the price decrease for memory, so just adding this much memory
> could be filed away as a reasonable assumption within 7.5 years (JDK
> 1.6.21 was released July 2010, I'm assuming that this is the age of the
> hardware as well (because why would you have installed this version on
> newer hardware, when newer releases existed)
> 
> I'm assuming that you have enough aspects to inspect - if you're really
> interested in finding the root cause, you'll need to come up with more
> specific measurements, e.g. profiler data, compare thread dumps and set
> up Tomcat 6 with Java 8 to have a third reference point.

I don't have Tomcat 6 to hand but I do have Tomcat 7. A quick test with
Tomcat 7 + Java 6 vs Tomcat 7 + Java 8 I saw a 20% increase in memory usage.

This looks very much like changes in the JVM rather than changes in Tomcat.

Mark

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