New gen should be big enough to handle all allocations that have a lifetime of a single request, considering that you'll have multiple concurrent requests. If new gen is routinely overflowed, you can put short-lived objects in the old gen.
Yes, you need to go to CMS. I have usually seen the hit rates on query results and doc caches to be fairly similar, with doc cache somewhat higher. Cache hit rates depend on the number of queries between updates. If you update once per day and get a million queries or so, your hit rates can get pretty good. 70-80% seems typical for doc cache on an infrequently updated index. We stay around 75% on our busiest 4m doc index. The query result cache is the most important, because it saves the most work. Ours stays around 20%, but I should spend some time improving that. The perm gen size is very big. I think we run with 128 Meg. wunder On Mar 2, 2014, at 10:54 PM, KNitin <nitin.t...@gmail.com> wrote: > Thanks, Walter > > Hit rate on the document caches is close to 70-80% and the filter caches > are a 100% hit (since most of our queries filter on the same fields but > have a different q parameter). Query result cache is not of great > importance to me since the hit rate their is almost negligible. > > Does it mean i need to increase the size of my filter and document cache > for large indices? > > The split up of my 25Gb heap usage is split as follows > > 1. 19 GB - Old Gen (100% pool utilization) > 2. 3 Gb - New Gen (50% pool utilization) > 3. 2.8 Gb - Perm Gen (I am guessing this is because of interned strings) > 4. Survivor space is in the order of 300-400 MB and is almost always 100% > full.(Is this a major issue?) > > We are also currently using Parallel GC collector but planning to move to > CMS for lesser stop-the-world gc times. If i increase the filter cache and > document cache entry sizes, they would also go to the Old gen right? > > A very naive question: How does increasing young gen going to help if we > know that solr is already pushing major caches and other objects to old gen > because of their nature? My young gen pool utilization is still well under > 50% > > > Thanks > Nitin > > > On Sun, Mar 2, 2014 at 9:31 PM, Walter Underwood <wun...@wunderwood.org>wrote: > >> An LRU cache will always fill up the old generation. Old objects are >> ejected, and those are usually in the old generation. >> >> Increasing the heap size will not eliminate this. It will make major, stop >> the world collections longer. >> >> Increase the new generation size until the rate of old gen increase slows >> down. Then choose a total heap size to control the frequency (and duration) >> of major collections. >> >> We run with the new generation at about 25% of the heap, so 8GB total and >> a 2GB newgen. >> >> A 512 entry cache is very small for query results or docs. We run with 10K >> or more entries for those. The filter cache size depends on your usage. We >> have only a handful of different filter queries, so a tiny cache is fine. >> >> What is your hit rate on the caches? >> >> wunder >> >> On Mar 2, 2014, at 7:42 PM, KNitin <nitin.t...@gmail.com> wrote: >> >>> Hi >>> >>> I have very large index for a few collections and when they are being >>> queried, i see the Old gen space close to 100% Usage all the time. The >>> system becomes extremely slow due to GC activity right after that and it >>> gets into this cycle very often >>> >>> I have given solr close to 30G of heap in a 65 GB ram machine and rest is >>> given to RAm. I have a lot of hits in filter,query result and document >>> caches and the size of all the caches is around 512 entries per >>> collection.Are all the caches used by solr on or off heap ? >>> >>> >>> Given this scenario where GC is the primary bottleneck what is a good >>> recommended memory settings for solr? Should i increase the heap memory >>> (that will only postpone the problem before the heap becomes full again >>> after a while) ? Will memory maps help at all in this scenario? >>> >>> >>> Kindly advise on the best practices >>> Thanks >>> Nitin >> >> >> -- Walter Underwood wun...@wunderwood.org
