Hi Jack,
Thanks for the feedback. My comments on the performance of the G1 collector
relate to its general performance, reading around suggests that generally
speaking the G1 collector isn't as performant as a combined CMS/UseParNewGC.
I've not tried it on an instance myself so don't know how well suited to
GeoServer it is. Any other insights you or anyone else has would be welcome.
Thanks,
Jonathan
---- On Mon, 16 May 2016 07:42:58 +0100 Jack Mitchell
<citricw...@gmail.com> wrote ----
Hi Jonathan,
We have been using the G1 Collector (on Java 8) in production for about a year
or so with no reported issues. When you mention the performance of G1, do you
mean in general or under GeoServer-specific workloads?
Thanks
Jack
On 14 May 2016 at 00:10, Jonathan Moules <jonathan-li...@lightpear.com>
wrote:
Hi List,
I was wondering if maybe the "Optimize your JVM" page could use an update?
(http://docs.geoserver.org/stable/en/user/production/container.html )
Reasoning:
"-XX:+UseParallelGC" - is enabled by default (although not on everything -
http://www.oracle.com/technetwork/java/javase/gc-tuning-6-140523.html#available_collectors
)
"-server" - is also enabled by default on almost everything that's going to be
used to run a production GeoServer.
And are the suggested options the best ones? Some thoughts from reading around
the subject, though I'm far from an expert:
- Should not the xmx and xms both be the same? Why initialise less than the
maximum in a production environment? - From
http://www.oracle.com/technetwork/java/javase/gc-tuning-6-140523.html -
"Setting -Xms and -Xmx to the same value increases predictability by removing
the most important sizing decision from the virtual machine. However, the
virtual machine is then unable to compensate if you make a poor choice."
- They are also rather low (though that's also based on the anticipated usage
and resource availability).
- The ParallelGC defaults are potentially prone to locking up GeoServer for a
while as it does the "stop-the-world" thing. This article (
http://blog.mgm-tp.com/2013/03/garbage-collection-tuning/ ) suggests that
turning off -XX:-UseAdaptiveSizePolicy reduces this somewhat when used with
-XX:NewSize=200m -XX:MaxNewSize=200m (or whatever values) (or NewRatio if we
don't want to specify a size).
Other options that it may be worth adding:
-XX:PermSize=256m and -XX:MaxPermSize=256m (or whatever is the best value).
Finally, has anyone tried the Concurrent Collector (CMS) with GeoServer?
Although that does seem to require more consideration with how its tweaked
(memory fragmentation doesn't look pleasant). The G1 Collector looks easier to
configure than CMS but doesn't appear to provide the same levels of performance.
What have others used that has worked (or not)?
Jonathan
p.s. (This may be better suited to the Dev list, but starting on User)
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bring their own devices (BYOD) to work are irked by the imposition of MDM
restrictions. Mobile Device Manager Plus allows you to control only the
apps on BYO-devices by containerizing them, leaving personal data untouched!
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