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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10326) Performance is worse in 3.0
Date Sat, 19 Sep 2015 18:41:04 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10326?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14877261#comment-14877261
] 

Benedict commented on CASSANDRA-10326:
--------------------------------------

So, [this comparison|http://cstar.datastax.com/graph?stats=518e5484-5ee3-11e5-b421-42010af0688f&metric=99.9th_latency&operation=1_user&smoothing=1&show_aggregates=true&xmin=0&xmax=865.37&ymin=0&ymax=158.51]
is especially interesting. With CASSANDRA-10322 now in, reverting GC settings to those we
have for 2.2 brings things much closer. 

* Latency drops across the board - we're now better than 2.2 for all latency metrics
* Throughput is still marginally worse for mixed, and latest queries
* Performance improves 40% for a point query, and 3.0 is now 10% _faster_ than 2.2 for these,
instead of 20% slower

As such, I would recommend that - until we can assess the GC behavioural changes further,
we revert CASSANDRA-7486

> Performance is worse in 3.0
> ---------------------------
>
>                 Key: CASSANDRA-10326
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10326
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Benedict
>            Priority: Critical
>             Fix For: 3.0.x
>
>
> Performance is generally turning out to be worse after 8099, despite a number of unrelated
performance enhancements being delivered. This isn't entirely unexpected, given a great deal
of time was spent optimising the old code, however things appear worse than we had hoped.
> My expectation was that workloads making extensive use of CQL constructs would be faster
post-8099, however the latest tests performed with very large CQL rows, including use of collections,
still exhibit performance below that of 2.1 and 2.2. 
> Eventually, as the dataset size grows large enough and the locality of access is just
right, the reduction in size of our dataset will yield a window during which some users will
perform better due simply to improved page cache hit rates. We seem to see this in some of
the tests. However we should be at least as fast (and really faster) off the bat.
> The following are some large partition benchmark results, with as many as 40K rows per
partition, running LCS. There are a number of parameters we can modify to see how behaviour
changes and under what scenarios we might still be faster, but the picture painted isn't brilliant,
and is consistent, so we should really try and figure out what's up before GA.
> [trades-with-flags (collections), blade11b|http://cstar.datastax.com/graph?stats=f0a17292-5a13-11e5-847a-42010af0688f&metric=op_rate&operation=1_user&smoothing=1&show_aggregates=true&xmin=0&xmax=4387.02&ymin=0&ymax=122951.4]
> [trades-with-flags (collections), blade11|http://cstar.datastax.com/graph?stats=e25aaaa0-5a13-11e5-ae0d-42010af0688f&metric=op_rate&operation=1_user&smoothing=1&show_aggregates=true&xmin=0&xmax=4424.75&ymin=0&ymax=130158.6]
> [trades (no collections), blade11|http://cstar.datastax.com/graph?stats=9b7da48e-570c-11e5-90fe-42010af0688f&metric=op_rate&operation=1_user&smoothing=1&show_aggregates=true&xmin=0&xmax=2682.46&ymin=0&ymax=142547.9]
> [~slebresne]: will you have time to look into this before GA?



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