Yes, the advice is intended to be "make it larger than the default". As I recall the default was a lot lower, like 4. This was on a Mac though. I am happy to make the default advice more like 12. The point is that almost all the memory is long-lived data structures so almost all the heap should be allocated to this. It ought to be tuned since the ratio of long-lived to short-lived objects is unusually high. YMMV but I'm sure the right value is at least 9.
On Thu, Nov 12, 2009 at 7:40 PM, Otis Gospodnetic <[email protected]> wrote: > Hello, > > Something on http://lucene.apache.org/mahout/taste.html#performance caught my > attention: > > -XX:+NewRatio=9: Increase heap allocated to 'old' objects, which is most of > them in this framework > > So I looked up this java parameter on > http://java.sun.com/javase/technologies/hotspot/vmoptions.jsp : > > > -XX:NewRatio=2 > Ratio of new/old generation sizes. [Sparc -client: 8; x86 -server: 8; x86 > -client: 12.]-client: 4 (1.3) 8 (1.3.1+), x86: 12] > > If I'm reading this correctly, the larger the number, the bigger portion of > the heap is used for "old" objects. > Also, it looks like different platforms have different defaults, so maybe > advising a single "9" value is not the right thing to do? > For example, it looks like on x86 the default is 12, so using NewRatio=9 > would actually decrease the space for old objects. > > I'd love to hear from anyone who actually knows what this means, how it > should be used, and if anyone has actually used different values with a large > Taste instance. > > Thanks, > Otis > -- > Sematext is hiring -- http://sematext.com/about/jobs.html?mls > Lucene, Solr, Nutch, Katta, Hadoop, HBase, UIMA, NLP, NER, IR > >
