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From Jay Kreps <jay.kr...@gmail.com>
Subject Re: benchmark kafka on 10GbE network
Date Tue, 25 Nov 2014 17:28:46 GMT
Yeah, neither of those are simple to optimize. The CRC is already the
optimized java crc we stole from Hadoop. It may be possible to make that
faster still but probably not easy. It might be possible to optimize out
some of the interrupt calls, though I'm not exactly sure.

One thing, though, is that the crc stuff should be highly paralellizable.
How many partitions/topics do you have? I suspect more writer threads (and
ensuring there are multiple partitions) would also improve throughput.
Basically we need to serialize writes per-partition which also involves
waiting on the crc, but this lock is per partition so if you have N
partitions N threads can all be working at once.

On Tue, Nov 25, 2014 at 3:03 AM, Manu Zhang <owenzhang1990@gmail.com> wrote:

> Thanks for the explanation.
>
> Here are some stats for I/O thread.
>
> *io-ratio 0.155*
> *io-time-ns-avg 16418.5*
> *io-wait-ratio 0.59*
> *io-wait-time-ns-avg  62881*
>
> It seems to confirm that IO spent much more time waiting than doing real
> work.
>
> Given the above stats, how could I trace down and pinpoint the bottleneck ?
> I guess computing crc32s can not be avoided.
>
> On Fri, Nov 21, 2014 at 12:34 PM, Jay Kreps <jay.kreps@gmail.com> wrote:
>
> > So I suspect that the bottleneck is actually in the writer thread (the
> one
> > calling send()), not the I/O thread. You could verify this by checking
> the
> > JMX stats which will give the amount of time the I/O thread spends
> waiting.
> > But since epollWait shows up first that is the I/O thread waiting for
> work.
> >
> > It looks like the big bottleneck is computing the crc32s for the
> messages.
> > The next big hit after that is signaling the I/O thread to wake-up and do
> > work.
> >
> > Here is an annotated version of those traces:
> >
> > These two are bogus and are just background JMX things I think:
> >  1 39.30% 39.30%   79585 300923 java.net.SocketInputStream.socketRead0
> >    2 20.62% 59.92%   41750 300450 java.net.PlainSocketImpl.socketAccept
> >
> > This is the I/O thread waiting for work to do
> >    3  9.52% 69.45%   19287 300660 sun.nio.ch.EPollArrayWrapper.epollWait
> >
> > These are the real problems:
> >    4  9.50% 78.94%   19234 300728 org.apache.kafka.common.
> > record.Record.computeChecksum
> >    5  4.14% 83.08%    8377 300777 sun.nio.ch.EPollArrayWrapper.interrupt
> >
> > I/O thread doing a write
> >    6  2.30% 85.38%    4662 300708 sun.nio.ch.FileDispatcherImpl.writev0
> >
> > This is a one time thing when fetching metadata on startup
> >    7  1.61% 86.99%    3260 300752
> > org.apache.kafka.clients.producer.KafkaProducer.waitOnMetadata
> >
> > These are all in the I/O thread so not relevant:
> >    8  1.24% 88.23%    2501 300804 sun.nio.ch.EPollArrayWrapper.epollWait
> >    9  1.08% 89.31%    2187 300734
> > org.apache.kafka.clients.producer.internals.RecordBatch.done
> >   10  0.98% 90.29%    1991 300870
> > org.apache.kafka.common.protocol.types.Type$6.write
> >   11  0.97% 91.26%    1961 300789
> > org.apache.kafka.clients.producer.internals.RecordAccumulator.ready
> >   12  0.96% 92.22%    1951 300726
> >
> > -Jay
> >
> > On Thu, Nov 20, 2014 at 5:42 PM, Manu Zhang <owenzhang1990@gmail.com>
> > wrote:
> >
> > > Ok, here is the hrpof output
> > >
> > > CPU SAMPLES BEGIN (total = 202493) Fri Nov 21 08:07:51 2014
> > > rank   self  accum   count trace method
> > >    1 39.30% 39.30%   79585 300923
> java.net.SocketInputStream.socketRead0
> > >    2 20.62% 59.92%   41750 300450 java.net.PlainSocketImpl.socketAccept
> > >    3  9.52% 69.45%   19287 300660
> sun.nio.ch.EPollArrayWrapper.epollWait
> > >    4  9.50% 78.94%   19234 300728
> > > org.apache.kafka.common.record.Record.computeChecksum
> > >    5  4.14% 83.08%    8377 300777
> sun.nio.ch.EPollArrayWrapper.interrupt
> > >    6  2.30% 85.38%    4662 300708 sun.nio.ch.FileDispatcherImpl.writev0
> > >    7  1.61% 86.99%    3260 300752
> > > org.apache.kafka.clients.producer.KafkaProducer.waitOnMetadata
> > >    8  1.24% 88.23%    2501 300804
> sun.nio.ch.EPollArrayWrapper.epollWait
> > >    9  1.08% 89.31%    2187 300734
> > > org.apache.kafka.clients.producer.internals.RecordBatch.done
> > >   10  0.98% 90.29%    1991 300870
> > > org.apache.kafka.common.protocol.types.Type$6.write
> > >   11  0.97% 91.26%    1961 300789
> > > org.apache.kafka.clients.producer.internals.RecordAccumulator.ready
> > >   12  0.96% 92.22%    1951 300726
> > > org.apache.kafka.common.record.MemoryRecords.append
> > >   13  0.89% 93.12%    1809 300829 java.nio.Bits.copyFromArray
> > >   14  0.75% 93.86%    1510 300722 java.nio.HeapByteBuffer.<init>
> > >   15  0.54% 94.41%    1100 300730
> > > org.apache.kafka.common.record.Compressor.put
> > >   16  0.54% 94.95%    1094 300749
> > > org.apache.kafka.clients.producer.internals.RecordAccumulator.append
> > >   17  0.38% 95.33%     771 300755
> > > org.apache.kafka.clients.producer.KafkaProducer.send
> > >   18  0.36% 95.69%     736 300830
> > > org.apache.kafka.common.metrics.Sensor.record
> > >   19  0.35% 96.04%     709 300848 sun.nio.ch.IOUtil.drain
> > >   20  0.33% 96.37%     665 300814 sun.nio.ch.IOUtil.drain
> > >   21  0.32% 96.69%     644 300812
> > > org.apache.kafka.common.metrics.Sensor.record
> > >   22  0.31% 97.00%     626 300725
> > > org.apache.kafka.clients.producer.internals.Partitioner.partition
> > >   23  0.28% 97.28%     571 300729
> > > org.apache.kafka.clients.producer.internals.RecordAccumulator.append
> > >   24  0.26% 97.54%     535 300764
> > > org.apache.log4j.Category.getEffectiveLevel
> > >   25  0.25% 97.79%     501 300924
> > > org.apache.kafka.common.protocol.types.Schema.write
> > >   26  0.19% 97.98%     392 300802
> > > org.apache.kafka.common.metrics.Sensor.record
> > >   27  0.19% 98.17%     386 300797
> > > org.apache.kafka.common.metrics.Sensor.record
> > >   28  0.17% 98.34%     342 300739
> > > org.apache.kafka.common.record.Record.write
> > >   29  0.16% 98.50%     315 300792
> > > org.apache.kafka.common.record.Record.write
> > >   30  0.15% 98.64%     294 300757
> > > org.apache.kafka.common.record.Record.write
> > >   31  0.12% 98.76%     238 300731
> > > org.apache.kafka.common.record.Record.write
> > >   32  0.09% 98.85%     180 300747
> > > org.apache.kafka.clients.producer.KafkaProducer.send
> > >   33  0.09% 98.94%     177 300750
> > > org.apache.kafka.common.record.Record.write
> > >   34  0.06% 98.99%     112 300851 sun.nio.ch.NativeThread.current
> > >   35  0.05% 99.05%     110 300753
> > > org.apache.kafka.clients.producer.KafkaProducer.send
> > >   36  0.05% 99.09%      93 300723 java.lang.System.arraycopy
> > >   37  0.04% 99.13%      80 300872
> > > org.apache.kafka.clients.tools.ProducerPerformance.main
> > >   38  0.04% 99.17%      78 300770 java.util.HashMap.getEntry
> > >   39  0.04% 99.21%      78 300859
> > > org.apache.kafka.clients.producer.internals.RecordAccumulator.append
> > >   40  0.04% 99.25%      73 300861 sun.nio.ch.EPollArrayWrapper.epollCtl
> > >   41  0.03% 99.28%      67 300718 sun.misc.Unsafe.copyMemory
> > >   42  0.03% 99.31%      59 300737
> > > org.apache.kafka.clients.producer.internals.Metadata.timeToNextUpdate
> > >   43  0.03% 99.33%      52 300816
> > > org.apache.kafka.clients.producer.internals.Metadata.fetch
> > >   44  0.02% 99.36%      48 300715 sun.nio.ch.FileDispatcherImpl.read0
> > >   45  0.02% 99.38%      42 300794
> > > org.apache.log4j.Category.getEffectiveLevel
> > >   46  0.02% 99.40%      41 300740
> > > org.apache.kafka.clients.producer.internals.Metadata.timeToNextUpdate
> > >   47  0.02% 99.42%      40 300795 sun.nio.ch.NativeThread.current
> > >   48  0.01% 99.43%      28 300785 sun.nio.ch.EPollArrayWrapper.epollCtl
> > >   49  0.01% 99.44%      25 301055 sun.nio.ch.EPollSelectorImpl.wakeup
> > >   50  0.01% 99.45%      22 300806 java.lang.Thread.currentThread
> > > CPU SAMPLES END
> > >
> > >
> > > On Fri, Nov 21, 2014 at 5:05 AM, Jay Kreps <jay.kreps@gmail.com>
> wrote:
> > >
> > > > Great. There is a single I/O thread per producer client that does the
> > > > sending so it could be either that the sender thread or that thread
> is
> > > just
> > > > pegged. One way to dive in and see what is happening is to add the
> > > command
> > > > line option
> > > > *  -agentlib:hprof=cpu=samples,depth=10*
> > > > This will tell us where the time is going. If you sent that around it
> > may
> > > > be informative.
> > > >
> > > > -Jay
> > > >
> > > >
> > > > On Thu, Nov 20, 2014 at 12:41 AM, Manu Zhang <
> owenzhang1990@gmail.com>
> > > > wrote:
> > > >
> > > > > Thanks Jay. The producer metrics from jconsole is quite helpful.
> > > > >
> > > > > I've switched to the new producer and run producer benchmark with
> > > > >
> > > > > */usr/lib/kafka/bin/kafka-run-class.sh
> > > > > org.apache.kafka.clients.tools.ProducerPerformance topic1 500000000
> > > 1000
> > > > -1
> > > > > acks=1
> bootstrap.servers=node1:9092,node2:9092,node3:9092,node4:9092
> > > > > buffer.memory=2097152000 batch.size=1000000 linger.ms
> > > > > <http://linger.ms>=100*
> > > > >
> > > > > so my message size is 1000 bytes (gave up on 100 bytes after
> > fruitless
> > > > > experiments) and I've deliberately batched outgoing messages with
> > the "
> > > > > linger.ms" conf. A single producer could send 300 MB/s on average
> > and
> > > 3
> > > > > producers almost saturated the network bandwidth. CPU is fully
> > utilized
> > > > for
> > > > > each producer thread. It seems that I can't go further in a single
> > > > > producer. Any thoughts ?
> > > > >
> > > > > Also, I've noticed this kafka-fast
> > > > > <https://github.com/gerritjvv/kafka-fast> project,
> > > > > who claimed producer throughput could reach 191975 K messages/s for
> > 1KB
> > > > > message on 10GbE network. The difference is that a producer is
> > created
> > > > per
> > > > > topic partition.
> > > > >
> > > > >
> > > > > On Wed, Nov 19, 2014 at 12:34 PM, Jay Kreps <jay.kreps@gmail.com>
> > > wrote:
> > > > >
> > > > > > Yeah this will involve some experimentation.
> > > > > >
> > > > > > The metrics are visible with jconsole or another jmx viewer.
> > > > > >
> > > > > > It may also be worth looking at the cpu usage per-thread (e.g.
> > start
> > > > top
> > > > > > and press 't' I think).
> > > > > >
> > > > > > Another simple test for broker vs client as the bottleneck is
> just
> > to
> > > > > start
> > > > > > another producer or consumer and see if that improves throughput
> > (if
> > > so
> > > > > it
> > > > > > is probably a client bottleneck).
> > > > > >
> > > > > > -Jay
> > > > > >
> > > > > > On Tue, Nov 18, 2014 at 4:44 PM, Manu Zhang <
> > owenzhang1990@gmail.com
> > > >
> > > > > > wrote:
> > > > > >
> > > > > > > Thanks Jay for the quick response.
> > > > > > >
> > > > > > > Yes, it's a single producer and consumer both configured
with
> > > > multiple
> > > > > > > threads but I'm not using the new producer.
> > > > > > > CPU is typically 50% utilized on client and merely used
on
> > broker.
> > > > > Disks
> > > > > > > aren't busy either as a lot of data are cached in memory.
> > > > > > > Would you please give a link for the producer metrics you
are
> > > > referring
> > > > > > to
> > > > > > > ?
> > > > > > >
> > > > > > > Thanks,
> > > > > > > Manu
> > > > > > >
> > > > > > > On Wed, Nov 19, 2014 at 2:39 AM, Jay Kreps <
> jay.kreps@gmail.com>
> > > > > wrote:
> > > > > > >
> > > > > > > > Hey Manu,
> > > > > > > >
> > > > > > > > I'm not aware of a benchmark on 10GbE. I'd love to
see that
> > > though.
> > > > > > > Diving
> > > > > > > > into the results may help us find bottlenecks hidden
by the
> > > slower
> > > > > > > network.
> > > > > > > >
> > > > > > > > Can you figure out where the bottleneck is in your
test? I
> > assume
> > > > > this
> > > > > > > is a
> > > > > > > > single producer and consumer instance and you are
using the
> new
> > > > > > producer
> > > > > > > as
> > > > > > > > in those benchmarks?
> > > > > > > >
> > > > > > > > This can be slightly tricky as it can be cpu or I/O
on either
> > the
> > > > > > clients
> > > > > > > > or the brokers. You basically have to look at top,
iostat,
> and
> > > the
> > > > > jmx
> > > > > > > > metrics for clues. The producer has good metrics that
explain
> > > > whether
> > > > > > it
> > > > > > > is
> > > > > > > > spending most of its time waiting or sending data.
Not sure
> if
> > > > there
> > > > > > is a
> > > > > > > > similar diagnostic for the consumer.
> > > > > > > >
> > > > > > > > -Jay
> > > > > > > >
> > > > > > > > On Tue, Nov 18, 2014 at 5:10 AM, Manu Zhang <
> > > > owenzhang1990@gmail.com
> > > > > >
> > > > > > > > wrote:
> > > > > > > >
> > > > > > > > > Hi all,
> > > > > > > > >
> > > > > > > > > I have been trying out kafka benchmarks described
in Jay's
> > > > > > > > >
> > > > > >
> > > benchmarking-apache-kafka-2-million-writes-second-three-cheap-machines
> > > > > > > > > <
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> https://engineering.linkedin.com/kafka/benchmarking-apache-kafka-2-million-writes-second-three-cheap-machine
> > > > > > > > > >.
> > > > > > > > > I'm able to get similar results on a 4-node GbE
network
> whose
> > > > > > in-bytes
> > > > > > > > > could be saturated at 120MB/s. However, on a
4-node, 10GbE
> > > > > network, I
> > > > > > > can
> > > > > > > > > not get in-bytes higher than 150MB/s. *Has anyone
> benchmarked
> > > > kafka
> > > > > > on
> > > > > > > a
> > > > > > > > > 10GbE network ? Any rule of thumb on 10GbE network
for
> > > > > configurations
> > > > > > > of
> > > > > > > > > broker, producer and consumer ? *
> > > > > > > > >
> > > > > > > > > My kafka version is 0.8.1.1 and I've created
a topic with 8
> > > > > > partitions
> > > > > > > > with
> > > > > > > > > 1 replica distributed evenly among the 4 nodes.
Message
> size
> > is
> > > > 100
> > > > > > > > bytes.
> > > > > > > > > I use all the default kafka settings.
> > > > > > > > > My cluster has 4 nodes, where each node has 32
cores, 128MB
> > RAM
> > > > > and 3
> > > > > > > > disks
> > > > > > > > > for kafka.
> > > > > > > > >
> > > > > > > > > I've tried increasing message size to 1000 bytes
which
> > improved
> > > > > > > > producer's
> > > > > > > > > throughput but not consumer's.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > Thanks,
> > > > > > > > > Manu
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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