>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 -- View this message in context: http://www.nabble.com/Performance-%22dead-zone%22-due-to-garbage-collect ion-tp21588427p21590150.html Sent from the Solr - User mailing list archive at Nabble.com.
