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https://issues.apache.org/jira/browse/CASSANDRA-13530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16011620#comment-16011620
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Yuji Ito commented on CASSANDRA-13530:
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Thanks Ariel, Hiroyuki,
As Ariel said, this CommitLogService will need tuning.
If you can increase the window size, the throughput increase at the higher
concurrency.
I show the result of various window size as below.
The result showed the batch window size as Hiroyuki pointed.
The throughput of the batch window 10ms was the same as the batch window 2ms.
h6. SELECT / sec
||\# of threads||batch 2ms||batch 10ms||group 10ms||group 15ms||
|1|192|192|103|75|
|2|163|169|212|150|
|4|264|263|416|310|
|8|454|454|800|563|
|16|744|744|1311|1081|
|32|1151|1155|1481|1916|
|64|1767|1772|1844|2922|
|128|2949|2962|3011|3192|
|256|4723|4785|5000|5213|
h6. UPDATE / sec
||\# of threads||batch 2ms||batch 10ms||group 10ms||group 15ms||
|1|45|45|26|18|
|2|39|38|51|36|
|4|58|58|102|71|
|8|102|98|198|139|
|16|167|171|213|268|
|32|289|279|295|314|
|64|544|540|548|570|
|128|1046|1050|1058|1098|
|256|2020|2026|2061|2204|
> GroupCommitLogService
> ---------------------
>
> Key: CASSANDRA-13530
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13530
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Yuji Ito
> Assignee: Yuji Ito
> Fix For: 2.2.x, 3.0.x, 3.11.x
>
> Attachments: groupCommit22.patch, groupCommit30.patch,
> groupCommit3x.patch, MicroRequestThread.java
>
>
> I propose a new CommitLogService, GroupCommitLogService, to improve the
> throughput when lots of requests are received.
> It improved the throughput by maximum 94%.
> I'd like to discuss about this CommitLogService.
> Currently, we can select either 2 CommitLog services; Periodic and Batch.
> In Periodic, we might lose some commit log which hasn't written to the disk.
> In Batch, we can write commit log to the disk every time. The size of commit
> log to write is too small (< 4KB). When high concurrency, these writes are
> gathered and persisted to the disk at once. But, when insufficient
> concurrency, many small writes are issued and the performance decreases due
> to the latency of the disk. Even if you use SSD, processes of many IO
> commands decrease the performance.
> GroupCommitLogService writes some commitlog to the disk at once.
> The patch adds GroupCommitLogService (It is enabled by setting
> `commitlog_sync` and `commitlog_sync_group_window_in_ms` in cassandra.yaml).
> The difference from Batch is just only waiting for the semaphore.
> By waiting for the semaphore, some writes for commit logs are executed at the
> same time.
> In GroupCommitLogService, the latency becomes worse if the there is no
> concurrency.
> I measured the performance with my microbench (MicroRequestThread.java) by
> increasing the number of threads.The cluster has 3 nodes (Replication factor:
> 3). Each nodes is AWS EC2 m4.large instance + 200IOPS io1 volume.
> The result is as below. The GroupCommitLogService with 10ms window improved
> update with Paxos by 94% and improved select with Paxos by 76%.
> h6. SELECT / sec
> ||\# of threads||Batch 2ms||Group 10ms||
> |1|192|103|
> |2|163|212|
> |4|264|416|
> |8|454|800|
> |16|744|1311|
> |32|1151|1481|
> |64|1767|1844|
> |128|2949|3011|
> |256|4723|5000|
> h6. UPDATE / sec
> ||\# of threads||Batch 2ms||Group 10ms||
> |1|45|26|
> |2|39|51|
> |4|58|102|
> |8|102|198|
> |16|167|213|
> |32|289|295|
> |64|544|548|
> |128|1046|1058|
> |256|2020|2061|
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