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https://issues.apache.org/jira/browse/CASSANDRA-14448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16505576#comment-16505576
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Dikang Gu commented on CASSANDRA-14448:
---------------------------------------
An initial patch here:
[trunk|https://github.com/DikangGu/cassandra/commit/da43bb7fc1336e8f2f7e04d84be1a44271eafba9].
It introduces a new PAXOS_PREPARE_AND_READ verb, to allow in-place upgrade.
I also ran some tests in our internal test cluster, which across 5 different
data centers in US, with 1 replica in each data center. The test client was
doing 10K operations.
I test two types of use cases, non-contention and contention ones. For
non-contention use case, each operation updates different key. For contention
use case, there are 5 unique keys in total, each thread picks one to update.
As the result, there is about +40% latency improvements for non-contention
test. For contention test, there are some latency improvements as well, and the
timeouts are much less as well.
non-contention test
| |C* 3.0.15, without patch|fastpaxos, combine prepare and read together| |
|10K CAS|sync commit|async commit|sync commit|async commit| |
| |1 thread|5 threads|10 threads|1 thread|5 threads|10 threads|1 thread|5
threads|10 threads|1 thread|5 threads|10 threads| |
|Total Time
(ms)|1915163|378791|185424|1464694|291807|140827|1422831|284674|142433|948230|187583|94047|
|
|mean|192.31|188.99|185.08|146.62|145.8|140.41|142.4|142.46|142.23|94.31|93.96|93.93|
|
|P75|196.52|195.6|194.99|148.08|147.29|146.68|147.46|147.06|146.81|98.86|98.27|98.2|
|
|P95|209.68|208.23|207.77|160.8|160.25|158.89|147.98|147.48|147.25|99.51|98.69|98.57|
|
|P99|211.43|212.21|208.61|161.71|160.94|159.9|148.42|147.85|147.6|100.18|99.12|98.86|
|
| | | | | | | | | | | | | | |
contention test
| |C* 3.0.15, without patch|fastpaxos, combine prepare and read together| |
|10K CAS|sync commit|async commit|sync commit|async commit| |
| |1 thread|5 threads|10 threads|1 thread|5 threads|10 threads|1 thread|5
threads|10 threads|1 thread|5 threads|10 threads| |
|Total Time
(ms)|1886023|364048|478343|1462954|450799|481059|1432742|285417|330649|937701|305705|304444|
|
|mean|193.41|183.24|510.41|148.48|232.41|493.72|143.28|143.91|334.54|95.55|154.45|301.69|
|
|P75|199.69|186.09|1008.11|150.5|150.49|1010.68|142.28|149.5|432.55|96.113|101.42|418.88|
|
|P95|200.58|187.09|1160.3|151.03|1029.75|1167.68|151.19|150.27|1076.05|102.11|615.83|1039.38|
|
|P99|201.17|189.71|1217.71|151.92|1146.28|1228.08|151.66|150.59|1141.52|102.65|1048.34|1129.77|
|
|Timeouts|0|0|2093|0|443|2282|0|0|863|0|193|752| |
| | | | | | | | | | | | | | |
> Improve the performance of CAS
> ------------------------------
>
> Key: CASSANDRA-14448
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14448
> Project: Cassandra
> Issue Type: Improvement
> Components: Coordination
> Reporter: Dikang Gu
> Assignee: Dikang Gu
> Priority: Major
>
> I'm working on some performance improvements of the lightweight transitions
> (compare and set).
>
> As you know, current CAS requires 4 round trips to finish, which is not
> efficient, especially in cross DC case.
> 1) Prepare
> 2) Quorum read current value
> 3) Propose new value
> 4) Commit
>
> I'm proposing the following improvements to reduce it to 2 round trips, which
> is:
> 1) Combine prepare and quorum read together, use only one round trip to
> decide the ballot and also piggyback the current value in response.
> 2) Propose new value, and then send out the commit request asynchronously, so
> client will not wait for the ack of the commit. In case of commit failures,
> we should still have chance to retry/repair it through hints or following
> read/cas events.
>
> After the improvement, we should be able to finish the CAS operation using 2
> rounds trips. There can be following improvements as well, and this can be a
> start point.
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