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From Alexander Dejanovski <a...@thelastpickle.com>
Subject Re: GC/CPU increase after upgrading to 3.0.14 (from 2.1.18)
Date Tue, 26 Sep 2017 09:14:04 GMT
Hi Thomas,

I wouldn't move to G1GC with small heaps (<24GB) but just looking at your
ticket I think that your new gen is way too small.
I get that it worked better in 2.1 in your case though, which would suggest
that the memory footprint is different between 2.1 and 3.0. It looks like
you're using batches extensively.
Hopefully you're aware that multi partition batches are discouraged because
they indeed create heap pressure and high coordination costs (on top of
batchlog writes/deletions), leading to more GC pauses.
With a 400MB new gen, you're very likely to have a lot of premature
promotions (especially with the default max tenuring threshold), which will
fill the old gen faster than necessary and is likely to trigger major GCs.

I'd suggest you re-run those tests with a 2GB new gen and compare results.
Know that with Cassandra you can easily go up to 40%-50% of your heap for
the new gen.

Cheers,


On Tue, Sep 26, 2017 at 10:58 AM Matope Ono <matope.ono@gmail.com> wrote:

> Hi. We met similar situation after upgrading from 2.1.14 to 3.11 in our
> production.
>
> Have you already tried G1GC instead of CMS? Our timeouts were mitigated
> after replacing CMS with G1GC.
>
> Thanks.
>
> 2017-09-25 20:01 GMT+09:00 Steinmaurer, Thomas <
> thomas.steinmaurer@dynatrace.com>:
>
>> Hello,
>>
>>
>>
>> I have now some concrete numbers from our 9 node loadtest cluster with
>> constant load, same infrastructure after upgrading to 3.0.14 from 2.1.18.
>>
>>
>>
>> We see doubled GC suspension time + correlating CPU increase. In short,
>> 3.0.14 is not able to handle the same load.
>>
>>
>>
>> I have created https://issues.apache.org/jira/browse/CASSANDRA-13900.
>> Feel free to request any further additional information on the ticket.
>>
>>
>>
>> Unfortunately this is a real show-stopper for us upgrading to 3.0.
>>
>>
>>
>> Thanks for your attention.
>>
>>
>>
>> Thomas
>>
>>
>>
>> *From:* Steinmaurer, Thomas [mailto:thomas.steinmaurer@dynatrace.com]
>> *Sent:* Freitag, 15. September 2017 13:51
>> *To:* user@cassandra.apache.org
>> *Subject:* RE: GC/CPU increase after upgrading to 3.0.14 (from 2.1.18)
>>
>>
>>
>> Hi Jeff,
>>
>>
>>
>> we are using native (CQL3) via Java DataStax driver (3.1). We also have
>> OpsCenter running (to be removed soon) via Thrift, if I remember correctly.
>>
>>
>>
>> As said, the write request latency for our keyspace hasn’t really
>> changed, so perhaps another one (system related, OpsCenter …?) is affected
>> or perhaps the JMX metric is reporting something differently now. J So
>> not a real issue for now hopefully, just popping up in our monitoring,
>> wondering what this may be.
>>
>>
>>
>> Regarding compression metadata memory usage drop. Right, storage engine
>> re-write could be a reason. Thanks.
>>
>>
>>
>> Still wondering about the GC/CPU increase.
>>
>>
>>
>> Thanks!
>>
>>
>>
>> Thomas
>>
>>
>>
>>
>>
>>
>>
>> *From:* Jeff Jirsa [mailto:jjirsa@gmail.com <jjirsa@gmail.com>]
>> *Sent:* Freitag, 15. September 2017 13:14
>> *To:* user@cassandra.apache.org
>> *Subject:* Re: GC/CPU increase after upgrading to 3.0.14 (from 2.1.18)
>>
>>
>>
>> Most people find 3.0 slightly slower than 2.1. The only thing that really
>> stands out in your email is the huge change in 95% latency - that's
>> atypical. Are you using thrift or native 9042)?  The decrease in
>> compression metadata offheap usage is likely due to the increased storage
>> efficiency of the storage engine (see Cassandra-8099).
>>
>>
>>
>>
>> --
>>
>> Jeff Jirsa
>>
>>
>>
>>
>> On Sep 15, 2017, at 2:37 AM, Steinmaurer, Thomas <
>> thomas.steinmaurer@dynatrace.com> wrote:
>>
>> Hello,
>>
>>
>>
>> we have a test (regression) environment hosted in AWS, which is used for
>> auto deploying our software on a daily basis and attach constant load
>> across all deployments. Basically to allow us to detect any regressions in
>> our software on a daily basis.
>>
>>
>>
>> On the Cassandra-side, this is single-node in AWS, m4.xlarge, EBS gp2, 8G
>> heap, CMS. The environment has also been upgraded from Cassandra 2.1.18 to
>> 3.0.14 at a certain point in time. Without running upgradesstables so far.
>> We have not made any additional JVM/GC configuration change when going from
>> 2.1.18 to 3.0.14 on our own, thus, any self-made configuration changes
>> (e.g. new gen heap size) for 2.1.18 are also in place with 3.0.14.
>>
>>
>>
>> What we see after a time-frame of ~ 7 days (so, e.g. should not be caused
>> by some sort of spiky compaction pattern) is an AVG increase in GC/CPU
>> (most likely correlating):
>>
>> ·         CPU: ~ 12% => ~ 17%
>>
>> ·         GC Suspension: ~ 1,7% => 3,29%
>>
>>
>>
>> In this environment not a big deal, but relatively we have a CPU increase
>> of ~ 50% (with increased GC most likely contributing). Something we have
>> deal with when going into production (going into larger, multi-node
>> loadtest environments first though).
>>
>>
>>
>> Beside the CPU/GC shift, we also monitor the following noticeable changes
>> (don’t know if they somehow correlate with the CPU/GC shift above):
>>
>> ·         Increased AVG Write Client Requests Latency (95th Percentile),
>> org.apache.cassandra.metrics.ClientRequest.Latency.Write: 6,05ms => 29,2ms,
>> but almost constant (no change in) write client request latency for our
>> particular keyspace only,
>> org.apache.cassandra.metrics.Keyspace.ruxitdb.WriteLatency
>>
>> ·         Compression metadata memory usage drop,
>> org.apache.cassandra.metrics.Keyspace.XXX.
>> CompressionMetadataOffHeapMemoryUsed: ~218MB => ~105MB => Good or bad?
>> Known?
>>
>>
>>
>> I know, looks all a bit vague, but perhaps someone else has seen
>> something similar when upgrading to 3.0.14 and can share their
>> thoughts/ideas. Especially the (relative) CPU/GC increase is something we
>> are curious about.
>>
>>
>>
>> Thanks a lot.
>>
>>
>>
>> Thomas
>>
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>> The contents of this e-mail are intended for the named addressee only. It
>> contains information that may be confidential. Unless you are the named
>> addressee or an authorized designee, you may not copy or use it, or
>> disclose it to anyone else. If you received it in error please notify us
>> immediately and then destroy it. Dynatrace Austria GmbH (registration
>> number FN 91482h) is a company registered in Linz whose registered office
>> is at 4040 Linz, Austria, Freistädterstraße 313
>> <https://maps.google.com/?q=4040+Linz,+Austria,+Freist%C3%A4dterstra%C3%9Fe+313&entry=gmail&source=g>
>> The contents of this e-mail are intended for the named addressee only. It
>> contains information that may be confidential. Unless you are the named
>> addressee or an authorized designee, you may not copy or use it, or
>> disclose it to anyone else. If you received it in error please notify us
>> immediately and then destroy it. Dynatrace Austria GmbH (registration
>> number FN 91482h) is a company registered in Linz whose registered office
>> is at 4040 Linz, Austria, Freistädterstraße 313
>> <https://maps.google.com/?q=4040+Linz,+Austria,+Freist%C3%A4dterstra%C3%9Fe+313&entry=gmail&source=g>
>>
>
> --
-----------------
Alexander Dejanovski
France
@alexanderdeja

Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com

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