Improved Java Memory/Performance Defaults

[Gabriel Nell]

Binary package hint: tomcat6

Forking an issue from #541520

The current default of a 128MB heap does not make sense. This was chosen when Java 1.4 had a default maximum heap size of 64MB. In Java 1.5 and later, the JVM will automatically size the heap based on available memory. So the current default setting actually unnecessarily sets a limit on the memory available to tomcat, when not setting anything at all would actually allow the modern JVMs to do a better job.

References:
http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#par_gc.ergonomics.default_size
http://java.sun.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html
http://java.sun.com/docs/hotspot/gc5.0/ergo5.html

***
initial heap size:
Larger of 1/64th of the machine's physical memory on the machine or some reasonable minimum. Before J2SE 5.0, the default initial heap size was a reasonable minimum, which varies by platform. You can override this default using the -Xms command-line option.

maximum heap size:
Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0, the default maximum heap size was 64MB. You can override this default using the -Xmx command-line option.
***

[Gabriel Nell (gabriel-nell)]

Attaching proposed patch.

[Chuck Short (zulcss)]

Thanks for the patch, which version is this for?

chuck

[Thierry Carrez (ttx)]

This will be for Maverick, and discussed at UDS in the "Tomcat improvements" session.

[Gabriel Nell (gabriel-nell)]

An additional possibility is to specify the JVM using the "-server" flag. Although Java also will auto-set this based on the machine "class", currently it will only choose the server JVM one machines with 2GB+ of RAM and 2 cores. Interestingly, the 32bit instances offered by EC2 (a popular choice for hosting web frontends) have 1.7GB of RAM, which would cause the client VM to be auto-selected.

http://java.sun.com/docs/hotspot/HotSpotFAQ.html#compiler_types
http://java.sun.com/j2se/1.5.0/docs/guide/vm/server-class.html

[Launchpad Janitor (janitor)]

This bug was fixed in the package tomcat8 - 8.0.37-1

---------------
tomcat8 (8.0.37-1) unstable; urgency=medium

  * Team upload.
  * New upstream release
  * Removed 0001-set-UTF-8-as-default-character-encoding.patch (fixed upstream)

 -- Emmanuel Bourg <email address hidden> Mon, 19 Sep 2016 09:37:33 +0200