> > I observe long running nodes have high non heap memory footprint then a > recently started node. That is the reason I am interested in find non heap > memory usage by Cassandra node. What could be the reason of high non heap > memory footprint in long running cluster? >
Memory utilisation grows over time as SSTables get read. From Cassandra 2.2 onwards SSTables get mapped to memory -- i.e. the data files get copied to memory to speed up reads. A newly restarted C* doesn't use as much memory because the data hasn't been read yet so are not mapped to memory. I would like to know why memory usage is high and is there way to control > it. Laxmikant already mentioned disk_access_mode previously. This was a hidden property in C* but CASSANDRA-8464 <https://issues.apache.org/jira/browse/CASSANDRA-8464> [1] changed the behaviour in C* 2.2 so I wrote this KB article <https://support.datastax.com/hc/en-us/articles/360027838911> to explain the memory issue in detail [2]. TL;DR -- set this in cassandra.yaml to only mmap() the index files so there's less memory used: disk_access_mode: mmap_index_only I want to monitor memory pressure, I want to check that if heap+non heap > usage goes above certain level then I can take certain action. In any case as Michael Shuler explained, your approach is problematic so try to follow his recommendations. Cheers! [1] https://issues.apache.org/jira/browse/CASSANDRA-8464 [2] https://support.datastax.com/hc/en-us/articles/360027838911
