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https://issues.apache.org/jira/browse/CASSANDRA-13896?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16441984#comment-16441984
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Michael Burman commented on CASSANDRA-13896:
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I don't think there's notable performance difference here compared to 3.10. The
scaling seems to be limited to around the same number of operations and adding
hardware does not change that (I also tried to match the hardware, but there's
no point in going beyond 16 cores as the limitation is at around 9 cores when
using this stress-profile). Single node.
> Improving Cassandra write performance
> ---------------------------------------
>
> Key: CASSANDRA-13896
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13896
> Project: Cassandra
> Issue Type: Improvement
> Components: Local Write-Read Paths
> Environment: Skylake server with 2 sockets, 192GB RAM, 3xPCIe SSDs
> OS: Centos 7.3
> Java: Oracle JDK1.8.0_121
> Reporter: Prince Nana Owusu Boateng
> Priority: Major
> Labels: Performance
> Fix For: 4.x
>
> Attachments: Screen Shot 2017-09-22 at 11.22.43 AM.png, Screen Shot
> 2017-09-22 at 3.31.09 PM.png
>
>
> During our Cassandra performance testing, we see high percentage of the CPU
> spent in *org.apache.cassandra.utils.memory.SlabAllocator.allocate(int,
> OpOrder Group) * method. Appears to be high contention of the
> *<nextFreeOffset>* atomic Integer in write workloads. This structure is
> used by the threads for keeping track of the region bytebuffer allocation.
> When the contention appears, adding more clients, modifications of write
> specific parameters does not change write throughput performance. Attached
> are the details of Java Flight Recorder (JFR), showing hot functions and also
> performance results. When we see this contention, we still have plenty of
> CPU and throughput left ( *<20%* Total average CPU utilization and *<11%*
> of the storage write total throughput). This occurs on Cassandra 3.10.0-src
> version using the Cassandra-Stress.
> Proposal:
> We will like to introduce a solution which eliminates the atomic operations
> on the *<nextFreeOffset>* atomic Integer. This implementation will allow
> concurrent allocation of bytebuffers without an atomic compareAndSet and
> incrementAndGet operations. The solution is expected to increase overall
> write performance while improving CPU utilization.
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