I have noticed that in Mahout's wiki
(https://cwiki.apache.org/MAHOUT/recommender-documentation.html), it
is recommended to set JVM setting -XX:-DisableExplicitGC

However in the book "Mahout in Action" Appendix A "JVM tuning" this
setting is not mentioned.

Assuming, I use out-of-the-box Mahout item- and user-based
recommenders embedded into servlets. I wonder if Mahout authors still
recommend to use this setting for better performance?

Thank you
Aleksei

It's very minor, and is irrelevant unless you are embedding the recommender
in another app, and that app may call System.gc(). You can ignore it or set
it as you like.

2011/12/14 Aleksei Udatšnõi <[EMAIL PROTECTED]>

> I have noticed that in Mahout's wiki
> (https://cwiki.apache.org/MAHOUT/recommender-documentation.html), it
> is recommended to set JVM setting -XX:-DisableExplicitGC
>
> However in the book "Mahout in Action" Appendix A "JVM tuning" this
> setting is not mentioned.
>
> Assuming, I use out-of-the-box Mahout item- and user-based
> recommenders embedded into servlets. I wonder if Mahout authors still
> recommend to use this setting for better performance?
>
> Thank you
> Aleksei
>

I ran into a case where this setting was very important.

I ran my recommender app in Apache Tomcat and used precomputed item
similarities that were held in memory (these occupied something like 2
or 3 GB if I recall correctly).

Tomcat (I used 5.5) ensures that each object is checked for GC at least
once per hour to battle known memory leaks of some popular libraries.
This stopped the JVM for several seconds each hour as lots of small
objects had to be checked which resulted in a violation of the response
time guarantees of the recommender.

Disabling explicit GC stopped this behavior and full GC was only
triggered, when the similarities are updated (which is perfectly ok).

--sebastian
On 14.12.2011 10:45, Aleksei Udat�n�i wrote:
> I have noticed that in Mahout's wiki
> (https://cwiki.apache.org/MAHOUT/recommender-documentation.html), it
> is recommended to set JVM setting -XX:-DisableExplicitGC
>
> However in the book "Mahout in Action" Appendix A "JVM tuning" this
> setting is not mentioned.
>
> Assuming, I use out-of-the-box Mahout item- and user-based
> recommenders embedded into servlets. I wonder if Mahout authors still
> recommend to use this setting for better performance?
>
> Thank you
> Aleksei