Re: Linux HugePages and mmap
mcasandra mohitanchlia at gmail.com writes: Thanks! I think it still is a good idea to enable HiugePages and use UseLargePageSize option in JVM. What do you think? I experimented with it. It was about 10% performance improvement. But this was on 100% row cache hit. On smaller cache hit ratios the performance gain will be smaller, I believe.
Linux HugePages and mmap
Currently, in cassandra.yaml disk_access_mode is set to auto but the recommendation seems to be to use 'mmap_index_only'. If we use HugePages then do we still need to worry about setting disk_access_mode to mmap? I am planning to enable HugePages and use -XX:+UseLargePages option in JVM. I had a very good experience using HugePages with Oracle. -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Linux-HugePages-and-mmap-tp6170193p6170193.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: Linux HugePages and mmap
On Mon, Mar 14, 2011 at 1:59 PM, mcasandra mohitanch...@gmail.com wrote: Currently, in cassandra.yaml disk_access_mode is set to auto but the recommendation seems to be to use 'mmap_index_only'. Wrong. The recommendation is to leave it on auto. If we use HugePages then do we still need to worry about setting disk_access_mode to mmap? I am planning to enable HugePages and use -XX:+UseLargePages option in JVM. I had a very good experience using HugePages with Oracle. HugePages has nothing to do with disk access mode. -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
Re: Linux HugePages and mmap
Jonathan Ellis-3 wrote: Wrong. The recommendation is to leave it on auto. this is where I see mmap recommended for index. http://wiki.apache.org/cassandra/StorageConfiguration http://wiki.apache.org/cassandra/StorageConfiguration Jonathan Ellis-3 wrote: HugePages has nothing to do with disk access mode. Can you explain little more? Isn't mmap pinning the process memory in RAM similar to HugePages? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Linux-HugePages-and-mmap-tp6170193p6170423.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: Linux HugePages and mmap
On Mon, Mar 14, 2011 at 3:01 PM, mcasandra mohitanch...@gmail.com wrote: Jonathan Ellis-3 wrote: Wrong. The recommendation is to leave it on auto. this is where I see mmap recommended for index. http://wiki.apache.org/cassandra/StorageConfiguration FTFY. HugePages has nothing to do with disk access mode. Can you explain little more? Isn't mmap pinning the process memory in RAM similar to HugePages? mmap is about mapping address space to data files. HugePages affects how the kernel tracks address space via TLB. It does NOT affect what is actually mapped there. http://wiki.apache.org/cassandra/FAQ#mmap http://lwn.net/Articles/374424/ -- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
Re: Linux HugePages and mmap
Thanks! I think it still is a good idea to enable HiugePages and use UseLargePageSize option in JVM. What do you think? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Linux-HugePages-and-mmap-tp6170193p6171008.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
