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https://issues.apache.org/jira/browse/KAFKA-3565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15248198#comment-15248198
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Jay Kreps commented on KAFKA-3565:
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I think [~becket_qin] noted a good possible explanation. The dominate thing for
single-client producer performance is the efficiency of batching. With the
default setting the producer only batches optimistically so counter-intuitively
when the server get's slows, there is more batching. Good batching results in
much lower CPU since there are fewer requests, but also better compression
which also improves CPU. This is super counter-intuitive but basically making
the server slower can result in dynamic improvements in batching that make it
faster! One example of this was in-flight requests. I think one test to confirm
this hypothesis would be to attempt to reproduce the problem with linger.ms=10
to force maximum batching to occur and see if the difference goes away or not.
> Producer's throughput lower with compressed data after KIP-31/32
> ----------------------------------------------------------------
>
> Key: KAFKA-3565
> URL: https://issues.apache.org/jira/browse/KAFKA-3565
> Project: Kafka
> Issue Type: Bug
> Reporter: Ismael Juma
> Priority: Critical
> Fix For: 0.10.0.0
>
>
> Relative offsets were introduced by KIP-31 so that the broker does not have
> to recompress data (this was previously required after offsets were
> assigned). The implicit assumption is that reducing CPU usage required by
> recompression would mean that producer throughput for compressed data would
> increase.
> However, this doesn't seem to be the case:
> {code}
> Commit: eee95228fabe1643baa016a2d49fb0a9fe2c66bd (one before KIP-31/32)
> test_id:
> 2016-04-15--012.kafkatest.tests.benchmark_test.Benchmark.test_producer_throughput.topic=topic-replication-factor-three.security_protocol=PLAINTEXT.acks=1.message_size=100.compression_type=snappy
> status: PASS
> run time: 59.030 seconds
> {"records_per_sec": 519418.343653, "mb_per_sec": 49.54}
> {code}
> Full results: https://gist.github.com/ijuma/0afada4ff51ad6a5ac2125714d748292
> {code}
> Commit: fa594c811e4e329b6e7b897bce910c6772c46c0f (KIP-31/32)
> test_id:
> 2016-04-15--013.kafkatest.tests.benchmark_test.Benchmark.test_producer_throughput.topic=topic-replication-factor-three.security_protocol=PLAINTEXT.acks=1.message_size=100.compression_type=snappy
> status: PASS
> run time: 1 minute 0.243 seconds
> {"records_per_sec": 427308.818848, "mb_per_sec": 40.75}
> {code}
> Full results: https://gist.github.com/ijuma/e49430f0548c4de5691ad47696f5c87d
> The difference for the uncompressed case is smaller (and within what one
> would expect given the additional size overhead caused by the timestamp
> field):
> {code}
> Commit: eee95228fabe1643baa016a2d49fb0a9fe2c66bd (one before KIP-31/32)
> test_id:
> 2016-04-15--010.kafkatest.tests.benchmark_test.Benchmark.test_producer_throughput.topic=topic-replication-factor-three.security_protocol=PLAINTEXT.acks=1.message_size=100
> status: PASS
> run time: 1 minute 4.176 seconds
> {"records_per_sec": 321018.17747, "mb_per_sec": 30.61}
> {code}
> Full results: https://gist.github.com/ijuma/5fec369d686751a2d84debae8f324d4f
> {code}
> Commit: fa594c811e4e329b6e7b897bce910c6772c46c0f (KIP-31/32)
> test_id:
> 2016-04-15--014.kafkatest.tests.benchmark_test.Benchmark.test_producer_throughput.topic=topic-replication-factor-three.security_protocol=PLAINTEXT.acks=1.message_size=100
> status: PASS
> run time: 1 minute 5.079 seconds
> {"records_per_sec": 291777.608696, "mb_per_sec": 27.83}
> {code}
> Full results: https://gist.github.com/ijuma/1d35bd831ff9931448b0294bd9b787ed
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