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https://issues.apache.org/jira/browse/KAFKA-2517?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14735711#comment-14735711
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Ismael Juma commented on KAFKA-2517:
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Implementing `SelChImpl` is undesirable as it's an internal implementation
class in the JDK. A better alternative, in my opinion, is to pass the
underlying `SocketChannel` to `transferTo`; Ben verified that this fixes the
problem before filing this ticket. I suggest we add a transfer-like method to
`TransportLayer`. In the `PlaintextTransportLayer` implementation, it should
use the underlying `socketChannel` instead of itself.
> Performance Regression post SSL implementation
> ----------------------------------------------
>
> Key: KAFKA-2517
> URL: https://issues.apache.org/jira/browse/KAFKA-2517
> Project: Kafka
> Issue Type: Bug
> Reporter: Ben Stopford
> Assignee: Ben Stopford
> Priority: Blocker
> Fix For: 0.8.3
>
>
> It would appear that we incurred a performance regression on submission of
> the SSL work affecting the performance of the new Kafka Consumer.
> Running with 1KB messages. Macbook 2.3 GHz Intel Core i7, 8GB, APPLE SSD
> SM256E. Single server instance. All local.
> kafka-consumer-perf-test.sh ... --messages 3000000 --new-consumer
> Pre-SSL changes (commit 503bd36647695e8cc91893ffb80346dd03eb0bc5)
> Steady state throughputs = 234.8 MB/s
> (2861.5913, 234.8261, 3000596, 246233.0543)
> Post-SSL changes (commit 13c432f7952de27e9bf8cb4adb33a91ae3a4b738)
> Steady state throughput = 178.1 MB/s
> (2861.5913, 178.1480, 3000596, 186801.7182)
> Implication is a 25% reduction in consumer throughput for these test
> conditions.
> This appears to be caused by the use of PlaintextTransportLayer rather than
> SocketChannel in FileMessageSet.writeTo() meaning a zero copy transfer is not
> invoked.
> Switching to the use of a SocketChannel directly in FileMessageSet.writeTo()
> yields the following result:
> Steady state throughput = 281.8 MB/s
> (2861.5913, 281.8191, 3000596, 295508.7650)
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