cassandra—使用ycsb进行基准测试时吞吐量和延迟之间的相关性

k4ymrczo  于 2021-06-15  发布在  Cassandra
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我正在使用ycsb对许多不同的nosql数据库进行基准测试。但是,在处理客户机线程的数量时,我很难解释吞吐量和延迟的结果。
例如,当使用16个客户端线程对cassandra运行workload a(50/50读取和更新)进行基准测试时,将执行以下命令:

bin/ycsb run cassandra-cql -p hosts=xx.xx.xx.xx -p recordcount=525600 -p operationcount=525600 -threads 16 -P workloads/workloada -s > workloada_525600_16_threads_run_res.txt

其输出如下:

[OVERALL], RunTime(ms), 62751
[OVERALL], Throughput(ops/sec), 8375.962136061577
[TOTAL_GCS_PS_Scavenge], Count, 64
[TOTAL_GC_TIME_PS_Scavenge], Time(ms), 289
[TOTAL_GC_TIME_%_PS_Scavenge], Time(%), 0.46055042947522745
[TOTAL_GCS_PS_MarkSweep], Count, 0
[TOTAL_GC_TIME_PS_MarkSweep], Time(ms), 0
[TOTAL_GC_TIME_%_PS_MarkSweep], Time(%), 0.0
[TOTAL_GCs], Count, 64
[TOTAL_GC_TIME], Time(ms), 289
[TOTAL_GC_TIME_%], Time(%), 0.46055042947522745
[READ], Operations, 262650
[READ], AverageLatency(us), 1844.6075042832667
[READ], MinLatency(us), 290
[READ], MaxLatency(us), 116159
[READ], 95thPercentileLatency(us), 3081
[READ], 99thPercentileLatency(us), 7551
[READ], Return=OK, 262650
[CLEANUP], Operations, 16
[CLEANUP], AverageLatency(us), 139458.5
[CLEANUP], MinLatency(us), 1
[CLEANUP], MaxLatency(us), 2232319
[CLEANUP], 95thPercentileLatency(us), 19
[CLEANUP], 99thPercentileLatency(us), 2232319
[UPDATE], Operations, 262950
[UPDATE], AverageLatency(us), 1764.8220193953223
[UPDATE], MinLatency(us), 208
[UPDATE], MaxLatency(us), 95807
[UPDATE], 95thPercentileLatency(us), 2901
[UPDATE], 99thPercentileLatency(us), 7031
[UPDATE], Return=OK, 262950

使用32个线程运行相同的操作,我得到:

[OVERALL], RunTime(ms), 51785
[OVERALL], Throughput(ops/sec), 10149.65723665154
[TOTAL_GCS_PS_Scavenge], Count, 124
[TOTAL_GC_TIME_PS_Scavenge], Time(ms), 310
[TOTAL_GC_TIME_%_PS_Scavenge], Time(%), 0.5986289466061601
[TOTAL_GCS_PS_MarkSweep], Count, 0
[TOTAL_GC_TIME_PS_MarkSweep], Time(ms), 0
[TOTAL_GC_TIME_%_PS_MarkSweep], Time(%), 0.0
[TOTAL_GCs], Count, 124
[TOTAL_GC_TIME], Time(ms), 310
[TOTAL_GC_TIME_%], Time(%), 0.5986289466061601
[READ], Operations, 262848
[READ], AverageLatency(us), 2947.844628834916
[READ], MinLatency(us), 363
[READ], MaxLatency(us), 194559
[READ], 95thPercentileLatency(us), 5079
[READ], 99thPercentileLatency(us), 11055
[READ], Return=OK, 262848
[CLEANUP], Operations, 32
[CLEANUP], AverageLatency(us), 69601.5625
[CLEANUP], MinLatency(us), 1
[CLEANUP], MaxLatency(us), 2228223
[CLEANUP], 95thPercentileLatency(us), 3
[CLEANUP], 99thPercentileLatency(us), 2228223
[UPDATE], Operations, 262752
[UPDATE], AverageLatency(us), 2881.930485781269
[UPDATE], MinLatency(us), 316
[UPDATE], MaxLatency(us), 203391
[UPDATE], 95thPercentileLatency(us), 4987
[UPDATE], 99thPercentileLatency(us), 10711
[UPDATE], Return=OK, 262752

总体运行时较低,因此吞吐量较高,但延迟也较高。
我不太确定如何解释这些结果,以及如何找到要运行的“适当”数量的客户端线程?

7cjasjjr

7cjasjjr1#

为了有一个合格的基准,你应该首先定义你的系统要达到的sla要求。假设您的工作负载模式是50/50wr/rd,sla要求是10k ops/sec吞吐量,99%的延迟<10毫秒。使用ycsb -target 标记以生成所需的吞吐量,并使用不同的线程计数来查看哪个线程满足您的sla需求。
当使用更多的线程时,吞吐量会增加(更多的操作/秒),这是很有意义的,但这是以延迟为代价的。您应该查看相关的数据库指标,尝试找出您的瓶颈-可能是:
客户机(需要一个更强大的客户机,或者使用更少线程但更多客户机的更好的并行性)
网络
db服务器(磁盘/ram-使用更强大的示例)。
您可以在这里阅读更多关于db基准测试的应做和不应做的事情

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