I tried to run "cassandra-stress" on some of my table as proposed by Jake Luciani.
For a simple table, this tool is able to perform 80000 read op/s with a few CPU consumption if I request the table by the PK(name, tenanted) Ex : TABLE : CREATE TABLE IF NOT EXISTS buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY (name, tenantid)); QUERY : select * from buckets where name = ? and tenantid = ? limit 1; TOP output for 900 threads on cassandra-stress : top - 13:17:09 up 173 days, 21:54, 4 users, load average: 11.88, 4.30, 2.76 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 71.4%us, 14.0%sy, 0.0%ni, 13.1%id, 0.0%wa, 0.0%hi, 1.5%si, 0.0%st Mem: 98894704k total, 96367436k used, 2527268k free, 15440k buffers Swap: 0k total, 0k used, 0k free, 88194556k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java <== Cassandra-stress 29160 cassandr 20 0 16.3g 4.8g 10m S 1.3 5.0 44:46.89 java <== Cassandra Now, If I run another query on a table that provides a list of buckets according to the owner, the number of op/s is divided by 2 (42000 op/s) and CPU consumption grow UP. Ex : TABLE : CREATE TABLE IF NOT EXISTS owner_to_buckets (tenantid varchar, name varchar, owner varchar, location varchar, description varchar, codeQuota varchar, creationDate timestamp, updateDate timestamp, PRIMARY KEY ((owner, tenantid), name)); QUERY : select * from owner_to_buckets where owner = ? and tenantid = ? limit 10; TOP output for 4 threads on cassandra-stress: top - 13:49:16 up 173 days, 22:26, 4 users, load average: 1.76, 1.48, 1.17 Tasks: 273 total, 1 running, 271 sleeping, 0 stopped, 1 zombie Cpu(s): 26.3%us, 8.0%sy, 0.0%ni, 64.7%id, 0.0%wa, 0.0%hi, 1.0%si, 0.0%st Mem: 98894704k total, 97512156k used, 1382548k free, 14580k buffers Swap: 0k total, 0k used, 0k free, 90413772k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 37m S 186.7 5.1 62:26.77 java <== Cassandra 50622 root 20 0 28.8g 469m 12m S 102.5 0.5 0:45.84 java <== Cassandra-stress TOP output for 271 threads on cassandra-stress: top - 13:57:03 up 173 days, 22:34, 4 users, load average: 4.67, 1.76, 1.25 Tasks: 272 total, 1 running, 270 sleeping, 0 stopped, 1 zombie Cpu(s): 81.5%us, 14.0%sy, 0.0%ni, 3.1%id, 0.0%wa, 0.0%hi, 1.3%si, 0.0%st Mem: 98894704k total, 94955936k used, 3938768k free, 15892k buffers Swap: 0k total, 0k used, 0k free, 85993676k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 38m S 430.0 5.1 82:31.80 java <== Cassandra 50622 root 20 0 29.1g 2.3g 12m S 343.4 2.4 17:51.22 java <== Cassandra-stress I have 4 tables with a composed PRIMARY KEY (two of them has 4 entries : 2 for the partition key, one for cluster column and one for sort column) Two of these tables are frequently read with the partition key because we want to list data of a given user, this should explain my CPU load according to the simple test done with Cassandra-stress ... How can I avoid this? Collections could be an option but the number of data per user is not limited and can easily exceed 200 entries. According to the Cassandra documentation, collections have a size limited to 64KB. So it is probably not a solution in my case. :( Regards, Eric De : Chris Lohfink [mailto:clohf...@blackbirdit.com] Envoyé : lundi 22 septembre 2014 22:03 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Its going to depend a lot on your data model but 5-6k is on the low end of what I would expect. N=RF=2 is not really something I would recommend. That said 93GB is not much data so the bottleneck may exist more in your data model, queries, or client. What profiler are you using? The cpu on the select/read is marked as RUNNABLE but its really more of a wait state that may throw some profilers off, it may be a red haring. --- Chris Lohfink On Sep 22, 2014, at 11:39 AM, Leleu Eric <eric.le...@worldline.com<mailto:eric.le...@worldline.com>> wrote: Hi, I'm currently testing Cassandra 2.0.9 (and since the last week 2.1) under some read heavy load... I have 2 cassandra nodes (RF : 2) running under CentOS 6 with 16GB of RAM and 8 Cores. I have around 93GB of data per node (one Disk of 300GB with SAS interface and a Rotational Speed of 10500) I have 300 active client threads and they request the C* nodes with a Consitency level set to ONE (I'm using the CQL datastax driver). During my tests I saw a lot of CPU consumption (70% user / 6%sys / 4% iowait / 20%idle). C* nodes respond to around 5000 op/s (sometime up to 6000op/s) I try to profile a node and at the first look, 60% of the CPU is passed in the "sun.nio.ch<http://sun.nio.ch/>" package. (SelectorImpl.select or Channel.read) I know that Benchmark results are highly dependent of the Dataset and use cases, but according to my point of view this CPU consumption is normal according to the load. Someone can confirm that point ? According to my Hardware configuration, can I expect to have more than 6000 read op/s ? Regards, Eric ________________________________ Ce message et les pièces jointes sont confidentiels et réservés à l'usage exclusif de ses destinataires. Il peut également être protégé par le secret professionnel. Si vous recevez ce message par erreur, merci d'en avertir immédiatement l'expéditeur et de le détruire. L'intégrité du message ne pouvant être assurée sur Internet, la responsabilité de Worldline ne pourra être recherchée quant au contenu de ce message. 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