Hi, A hint : depending on your data set size + your request rate per second, 8 GB of RAM may be too low. And then, CPU might be high due to too frequent GC.
More RAM may bring: · More space for OS FS to cache the SSTable files in memory. · A greater heap size, and then, less frequent object promotion (young=>old space) and then, less major GC. Dominique [@@ THALES GROUP INTERNAL @@] De : D. Salvatore [mailto:dd.salvat...@gmail.com] Envoyé : mercredi 4 janvier 2017 16:28 À : user@cassandra.apache.org Objet : Cassandra CPU perfomance Hi, I deployed a Cassandra 2.2 ring composed by 4 nodes in the cloud with 8 vCPU and 8GB of ram. I am running some tests now with cassandra-stress and YCSB tools to test its performance. I am mainly interested in read requests with a small amount of write requests (95%/5%). Running the experiments, I noticed that even setting a high number of threads (or clients) the CPU (and disk) does not saturate, but still always around the 60% of utilisation. I am trying to figure out where is the bottleneck in my system. From the hardware point of view it seems all ok to me. I also looked into the Cassandra configuration file to see if there are some tuning parameters to increase the system throughput. I increase the value of concurrent_read/write parameter, but it doesn't increase the performance. The log file also does not contain any warning. What it could be that is limiting my system? Thanks
