Have you tried different sizes for the nursery? It should be several times larger than the per-request garbage.
Also, check your cache sizes. Objects evicted from the cache are almost always tenured, so those will add to the time needed for a full GC. Guess who was tuning GC for a week or two in December ... wunder On 1/21/09 12:15 PM, "Feak, Todd" <todd.f...@smss.sony.com> wrote: > From a high level view, there is a certain amount of garbage collection > that must occur. That garbage is generated per request, through a > variety of means (buffers, request, response, cache expulsion). The only > thing that JVM parameters can address is *when* that collection occurs. > > It can occur often in small chunks, or rarely in large chunks (or > anywhere in between). If you are CPU bound (which it sounds like you may > be), then you really have a decision to make. Do you want an overall > drop in performance, as more time is spent garbage collecting, OR do you > want spikes in garbage collection that are more rare, but have a > stronger impact. Realistically it becomes a question of one or the > other. You *must* pay the cost of garbage collection at some point in > time. > > It is possible that increasing cache size will decrease overall garbage > collection, as the churn caused by caused by cache misses creates > additional garbage. Decreasing the churn could decrease garbage. BUT, > this really depends on your cache hit rates. If they are pretty high > (>90%) then it's probably not much of a factor. However, if you are in > the 50%-60% range, larger caches may help you in a number of ways. > > -Todd Feak > > -----Original Message----- > From: wojtekpia [mailto:wojte...@hotmail.com] > Sent: Wednesday, January 21, 2009 11:14 AM > To: solr-user@lucene.apache.org > Subject: Re: Performance "dead-zone" due to garbage collection > > > I'm using a recent version of Sun's JVM (6 update 7) and am using the > concurrent generational collector. I've tried several other collectors, > none > seemed to help the situation. > > I've tried reducing my heap allocation. The search performance got worse > as > I reduced the heap. I didn't monitor the garbage collector in those > tests, > but I imagine that it would've gotten better. (As a side note, I do lots > of > faceting and sorting, I have 10M records in this index, with an > approximate > index file size of 10GB). > > This index is on a single machine, in a single Solr core. Would > splitting it > across multiple Solr cores on a single machine help? I'd like to find > the > limit of this machine before spreading the data to more machines. > > Thanks, > > Wojtek
