RE: CPU consumption of Cassandra
Thanks for all your comments, you help me a lot. My composite partition key is clearly the bottleneck (PRIMARY KEY ((owner, tenantid), name)) ) When I ran Cassandra-stress (on a dedicated server), the number of reads can’t go further than 10K/s (with idle to 20% / user to 72% and sys to 8%) If I create another table with a non-composed partition key, the number of reads reach 77K/s (with idle to 5% / user to 88% and sys to 6%) I guess I don’t have enough data to use a composed partition key. I will concatenate the two fields value in my application and it will probably increase my throughput. Regards, Eric De : DuyHai Doan [mailto:doanduy...@gmail.com] Envoyé : mercredi 24 septembre 2014 00:10 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Nice catch Daniel. The comment from Sylvain explains a lot ! On Tue, Sep 23, 2014 at 11:33 PM, Daniel Chia danc...@coursera.orgmailto:danc...@coursera.org wrote: If I had to guess, it might be in part i could be due to inefficiencies in 2.0 with regards to CompositeType (which is used in CQL3 tables) - https://issues.apache.org/jira/browse/CASSANDRA-5417?focusedCommentId=13821243page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13821243 Ticket reports 45% performance increase in reading slices compared to trunk in 2.1 Thanks, Daniel On Tue, Sep 23, 2014 at 5:08 PM, DuyHai Doan doanduy...@gmail.commailto:doanduy...@gmail.com wrote: I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our partial conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just assumptions and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.commailto:clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.commailto:eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.commailto:clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.orgmailto:user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes
Re: CPU consumption of Cassandra
More details on the composite partition key and usage of IN. I'm not sure whether your stress tests are using the IN clause with partition key, but this post is worth reading to avoid some caveats if you're planning to use composite partition keys in the future : http://getprismatic.com/story/1411447242054?share=MjE1ODA.MTQxMTQ0NzI0MjA1NA.iq0fmqRPn6t7KLIMFz5wh11BwYI On Wed, Sep 24, 2014 at 11:44 AM, Leleu Eric eric.le...@worldline.com wrote: Thanks for all your comments, you help me a lot. My composite partition key is clearly the bottleneck (PRIMARY KEY ((owner, tenantid), name)) ) When I ran Cassandra-stress (on a dedicated server), the number of reads can’t go further than 10K/s (with idle to 20% / user to 72% and sys to 8%) If I create another table with a non-composed partition key, the number of reads reach 77K/s (with idle to 5% / user to 88% and sys to 6%) I guess I don’t have enough data to use a composed partition key. I will concatenate the two fields value in my application and it will probably increase my throughput. Regards, Eric *De :* DuyHai Doan [mailto:doanduy...@gmail.com] *Envoyé :* mercredi 24 septembre 2014 00:10 *À :* user@cassandra.apache.org *Objet :* Re: CPU consumption of Cassandra Nice catch Daniel. The comment from Sylvain explains a lot ! On Tue, Sep 23, 2014 at 11:33 PM, Daniel Chia danc...@coursera.org wrote: If I had to guess, it might be in part i could be due to inefficiencies in 2.0 with regards to CompositeType (which is used in CQL3 tables) - https://issues.apache.org/jira/browse/CASSANDRA-5417?focusedCommentId=13821243page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13821243 Ticket reports 45% performance increase in reading slices compared to trunk in 2.1 Thanks, Daniel On Tue, Sep 23, 2014 at 5:08 PM, DuyHai Doan doanduy...@gmail.com wrote: I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing
RE: CPU consumption of Cassandra
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 8 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 %MEMTIME+ 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 %MEMTIME+ 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 %MEMTIME+ 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.commailto: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
Re: CPU consumption of Cassandra
Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com wrote: 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 8 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 %MEMTIME+ COMMAND 25857 root 20 0 29.7g 1.5g 12m S 693.0 1.6 38:45.58 java ç Cassandra-stress 29160 cassandr 20 0 16.3g 4.8g 10m S 1.3 5.0 44:46.89 java ç 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 %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 37m S 186.7 5.1 62:26.77 java ç Cassandra 50622 root 20 0 28.8g 469m 12m S 102.5 0.5 0:45.84 java ç 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 %MEMTIME+ COMMAND 29160 cassandr 20 0 13.6g 4.8g 38m S 430.0 5.1 82:31.80 java ç Cassandra 50622 root 20 0 29.1g 2.3g 12m S 343.4 2.4 17:51.22 java ç 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. L 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
RE : CPU consumption of Cassandra
First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.commailto:eric.le...@worldline.com wrote: 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 8 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 %MEMTIME+ 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 %MEMTIME+ 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
Re: CPU consumption of Cassandra
CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.commailto:eric.le...@worldline.com wrote: 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 8 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 %MEMTIME+ 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 %MEMTIME
Re: CPU consumption of Cassandra
I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com mailto:eric.le...@worldline.com eric.le...@worldline.com wrote: 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 8 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 %MEMTIME+ 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
Re: CPU consumption of Cassandra
If I had to guess, it might be in part i could be due to inefficiencies in 2.0 with regards to CompositeType (which is used in CQL3 tables) - https://issues.apache.org/jira/browse/CASSANDRA-5417?focusedCommentId=13821243page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13821243 Ticket reports 45% performance increase in reading slices compared to trunk in 2.1 Thanks, Daniel On Tue, Sep 23, 2014 at 5:08 PM, DuyHai Doan doanduy...@gmail.com wrote: I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com mailto:eric.le...@worldline.com eric.le...@worldline.com wrote: 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 8 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
Re: CPU consumption of Cassandra
Nice catch Daniel. The comment from Sylvain explains a lot ! On Tue, Sep 23, 2014 at 11:33 PM, Daniel Chia danc...@coursera.org wrote: If I had to guess, it might be in part i could be due to inefficiencies in 2.0 with regards to CompositeType (which is used in CQL3 tables) - https://issues.apache.org/jira/browse/CASSANDRA-5417?focusedCommentId=13821243page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13821243 Ticket reports 45% performance increase in reading slices compared to trunk in 2.1 Thanks, Daniel On Tue, Sep 23, 2014 at 5:08 PM, DuyHai Doan doanduy...@gmail.com wrote: I had done some benching in the past when we faced high CPU usage even though data set is very small, sitting entirely in memory, read the report there: https://github.com/doanduyhai/Cassandra_Data_Model_Bench Our *partial *conclusion were: 1) slice query fetching a page of 64kb of data and decoding columns is more CPU-expensive than a single read by column 2) the decoding of CompositeType costs more CPU for CQL3 data model than for old Thrift column family 3) since the Cell type for all CQL3 table is forced to BytesType to support any type of data, serialization/de-serialization may have a cost on CPU. The issue Eric Leleu is facing reminds me of point 1). When he puts limit to 1, it's a single read by column. The other query with limit 10 is translated internally to a slice query and may explain the CPU difference Now, do not take my words as granted. Those points are just *assumptions *and partial conclusions. I need extensive in depth debugging to confirm those. Did not have time lately. On Tue, Sep 23, 2014 at 10:46 PM, Chris Lohfink clohf...@blackbirdit.com wrote: CPU consumption may be affected from the cassandra-stress tool in 2nd example as well. Running on a separate system eliminates it as a possible cause. There is a little extra work but not anything that I think would be that obvious. tracing (can enable with nodetool) or profiling (ie with yourkit) can give more exposure to the bottleneck. Id run test from separate system first. --- Chris Lohfink On Sep 23, 2014, at 12:48 PM, Leleu Eric eric.le...@worldline.com wrote: First of all, Thanks for your help ! :) Here is some details : With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term I will test with more nodes, (4 with RF = 2) but for now I'm limited to 2 nodes for non technical reason ... Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. I performed the test in a new Keyspace in order to have a clear dataset. the 2nd query since its returning 10x the data and there will be more to go through within the partition I configured cassandra-stress in a way of each user has only one bucket so the amount of data is the same in the both case. (select * from buckets where name = ? and tenantid = ? limit 1 and select * from owner_to_buckets where owner = ? and tenantid = ? limit 10). Does cassandra perform extra read when the limit is bigger than the available data (even if the partition key contains only one single value in the clustering column) ? If the amount of data is the same, how can we explain the difference of CPU consumption? Regards, Eric De : Chris Lohfink [clohf...@blackbirdit.com] Date d'envoi : mardi 23 septembre 2014 19:23 À : user@cassandra.apache.org Objet : Re: CPU consumption of Cassandra Well, first off you shouldn't run stress tool on the node your testing. Give it its own box. With RF=N=2 your essentially testing a single machine locally which isnt the best indicator long term (optimizations available when reading data thats local to the node). 80k/sec on a system is pretty good though, your probably seeing slower on the 2nd query since its returning 10x the data and there will be more to go through within the partition. 42k/sec is still acceptable imho since these are smaller boxes. You are probably seeing high CPU because the system is doing a lot :) If you want to get more out of these systems can do some tuning probably, enable trace to see whats actually the bottleneck. Collections will very likely hurt more then help. --- Chris Lohfink On Sep 23, 2014, at 9:39 AM, Leleu Eric eric.le...@worldline.com mailto:eric.le...@worldline.com eric.le...@worldline.com wrote: 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 8 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
CPU consumption of Cassandra
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 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 pi?ces jointes sont confidentiels et r?serv?s ? l'usage exclusif de ses destinataires. Il peut ?galement ?tre prot?g? par le secret professionnel. Si vous recevez ce message par erreur, merci d'en avertir imm?diatement l'exp?diteur et de le d?truire. L'int?grit? du message ne pouvant ?tre assur?e sur Internet, la responsabilit? de Worldline ne pourra ?tre recherch?e quant au contenu de ce message. Bien que les meilleurs efforts soient faits pour maintenir cette transmission exempte de tout virus, l'exp?diteur ne donne aucune garantie ? cet ?gard et sa responsabilit? ne saurait ?tre recherch?e pour tout dommage r?sultant d'un virus transmis. This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Worldline liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted.
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 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” 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. Bien que les meilleurs efforts soient faits pour maintenir cette transmission exempte de tout virus, l'expéditeur ne donne aucune garantie à cet égard et sa responsabilité ne saurait être recherchée pour tout dommage résultant d'un virus transmis. This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Worldline liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted.
Re: CPU consumption of Cassandra
Eric, We have a new stress tool to help you share your schema for wider bench marking. see http://www.datastax.com/dev/blog/improved-cassandra-2-1-stress-tool-benchmark-any-schema If you wouldn't mind creating a yaml for your schema I would be happy to take a look. -Jake On Mon, Sep 22, 2014 at 12:39 PM, Leleu Eric 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” 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. Bien que les meilleurs efforts soient faits pour maintenir cette transmission exempte de tout virus, l'expéditeur ne donne aucune garantie à cet égard et sa responsabilité ne saurait être recherchée pour tout dommage résultant d'un virus transmis. This e-mail and the documents attached are confidential and intended solely for the addressee; it may also be privileged. If you receive this e-mail in error, please notify the sender immediately and destroy it. As its integrity cannot be secured on the Internet, the Worldline liability cannot be triggered for the message content. Although the sender endeavours to maintain a computer virus-free network, the sender does not warrant that this transmission is virus-free and will not be liable for any damages resulting from any virus transmitted. -- http://twitter.com/tjake
