Hi, I would like to have some advices on best practices related to Heap Size, MMap, direct memory, GC algorithm and OS Swap.
This is a waste subject and sorry for this long question but all these items are linked in order to have a stable Solr environment. My understanding and questions. About JVM heap size setting JVM heap size setting is related to use case so there is no other advice than reduce it at the minimum possible size in order to avoid GC issue. Reduce Heap size at is minimum will be achieved mainly by : - Optimize schema by remove unused fields and not index / store fields if it is not necessary - Enable docValues on fields used for facetting, sorting and grouping - Not oversize Solr cache - Be careful with rows and fl query parameters Any other advice is welcome :) About MMap setting According to the great article “ http://blog.thetaphi.de/2012/07/use-lucenes-mmapdirectory-on-64bit.html” from Uwe Schindler, the only tasks that have to be done at OS settings level is check that “ulimit -v” and “ulimit -m” both report “unlimited” and increase vm.max_map_count setting from is default 65536. I suppose the best value is related to available off heap memory. I generally set it to 262144. Is it a good value or is there a better way to determine this value ? About Direct Memory According to a response in Solr Maillig list from Uwe Schindler (again), I understand that the MmapDirectory is not Direct Memory. The only place where I read that MaxDirectMemorySize JVM setting have to be set for Solr is in Cloudera blog post and in Solr mailing list when using Solr with HDFS. Is it necessary to change the default MaxDirectMemorySize JVM setting ? If yes, how to determine the appropriate value ? About OS Swap setting Linux generally starts swapping when less than 30% of the memory is free. In order to avoid OS goes against Solr for off heap memory management, I use to change OS swappiness value to 0. Can you confirm it is a good thing ? About CMS GC vs G1 GC Default Solr setting use CMS GC. According to the post from Shawn Heisey in the old Solr wiki ( https://wiki.apache.org/solr/ShawnHeisey), can we consider that G1 GC can definitely be used with Solr for heap size over nearly 4Gb ? Regards Dominique -- Dominique Béjean 06 08 46 12 43
