ScyllaDB engineer here.

C++ is really an enabling technology here. It is directly responsible for a small fraction of the gain by executing faster than Java. But it is indirectly responsible for the gain by allowing us direct control over memory and threading. Just as an example, Scylla starts by taking over almost all of the machine's memory, and dynamically assigning it to memtables, cache, and working memory needed to handle requests in flight. Memory is statically partitioned across cores, allowing us to exploit NUMA fully. You can't do these things in Java.

I would say the major contributors to Scylla performance are:
 - thread-per-core design
 - replacement of the page cache with a row cache
- careful attention to many small details, each contributing a little, but with a large overall impact

While I'm here I can say that performance is not the only goal here, it is stable and predictable performance over varying loads and during maintenance operations like repair, without any special tuning. We measure the amount of CPU and I/O spent on foreground (user) and background (maintenance) tasks and divide them fairly. This work is not complete but already makes operating Scylla a lot simpler.

On 03/10/2017 01:42 AM, Kant Kodali wrote:
I dont think ScyllaDB performance is because of C++. The design decisions in scylladb are indeed different from Cassandra such as getting rid of SEDA and moving to TPC and so on.

If someone thinks it is because of C++ then just show the benchmarks that proves it is indeed the C++ which gave 10X performance boost as ScyllaDB claims instead of stating it.


On Thu, Mar 9, 2017 at 3:22 PM, Richard L. Burton III <mrbur...@gmail.com <mailto:mrbur...@gmail.com>> wrote:

    They spend an enormous amount of time focusing on performance. You
    can expect them to continue on with their optimization and keep
    crushing it.

    P.S., I don't work for ScyllaDB.

    On Thu, Mar 9, 2017 at 6:02 PM, Rakesh Kumar
    <rakeshkumar...@outlook.com <mailto:rakeshkumar...@outlook.com>>
    wrote:

        In all of their presentation they keep harping on the fact
        that scylladb is written in C++ and does not carry the
        overhead of Java.  Still the difference looks staggering.
        ________________________________________
        From: daemeon reiydelle <daeme...@gmail.com
        <mailto:daeme...@gmail.com>>
        Sent: Thursday, March 9, 2017 14:21
        To: user@cassandra.apache.org <mailto:user@cassandra.apache.org>
        Subject: Re: scylladb

        The comparison is fair, and conservative. Did substantial
        performance comparisons for two clients, both results returned
        throughputs that were faster than the published comparisons
        (15x as I recall). At that time the client preferred to
        utilize a Cass COTS solution and use a caching solution for
        OLA compliance.


        .......

        Daemeon C.M. Reiydelle
        USA (+1) 415.501.0198 <tel:%28%2B1%29%20415.501.0198>
        London (+44) (0) 20 8144 9872
        <tel:%28%2B44%29%20%280%29%2020%208144%209872>

        On Thu, Mar 9, 2017 at 11:04 AM, Robin Verlangen <ro...@us2.nl
        <mailto:ro...@us2.nl><mailto:ro...@us2.nl
        <mailto:ro...@us2.nl>>> wrote:
        I was wondering how people feel about the comparison that's
        made here between Cassandra and ScyllaDB :
        
http://www.scylladb.com/technology/ycsb-cassandra-scylla/#results-of-3-scylla-nodes-vs-30-cassandra-nodes
        
<http://www.scylladb.com/technology/ycsb-cassandra-scylla/#results-of-3-scylla-nodes-vs-30-cassandra-nodes>

        They are claiming a 10x improvement, is that a fair comparison
        or maybe a somewhat coloured view of a (micro)benchmark in a
        specific setup? Any pros/cons known?

        Best regards,

        Robin Verlangen
        Chief Data Architect

        Disclaimer: The information contained in this message and
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        On Wed, Dec 16, 2015 at 11:52 AM, Carlos Rolo
        <r...@pythian.com
        <mailto:r...@pythian.com><mailto:r...@pythian.com
        <mailto:r...@pythian.com>>> wrote:
        No rain at all! But I almost had it running last weekend, but
        stopped short of installing it. Let's see if this one is for real!

        Regards,

        Carlos Juzarte Rolo
        Cassandra Consultant

        Pythian - Love your data

        rolo@pythian | Twitter: @cjrolo | Linkedin:
        linkedin.com/in/carlosjuzarterolo
        
<http://linkedin.com/in/carlosjuzarterolo><http://linkedin.com/in/carlosjuzarterolo
        <http://linkedin.com/in/carlosjuzarterolo>>
        Mobile: +351 91 891 81 00
        <tel:%2B351%2091%20891%2081%2000><tel:+351%20918%20918%20100>
        | Tel: +1 613 565 8696 x1649
        <tel:%2B1%20613%20565%208696%20x1649><tel:+1%20613-565-8696>
        www.pythian.com
        <http://www.pythian.com><http://www.pythian.com/
        <http://www.pythian.com/>>

        On Wed, Dec 16, 2015 at 12:38 AM, Dani Traphagen
        <dani.trapha...@datastax.com
        <mailto:dani.trapha...@datastax.com><mailto:dani.trapha...@datastax.com
        <mailto:dani.trapha...@datastax.com>>> wrote:
        You'll be the first Carlos.

        [Inline image 1]

        Had any rain lately? Curious how this went, if so.

        On Thu, Nov 12, 2015 at 4:36 AM, Jack Krupansky
        <jack.krupan...@gmail.com
        <mailto:jack.krupan...@gmail.com><mailto:jack.krupan...@gmail.com
        <mailto:jack.krupan...@gmail.com>>> wrote:
        I just did a Twitter search on scylladb and did not see any
        tweets about actual use, so far.


        -- Jack Krupansky

        On Wed, Nov 11, 2015 at 10:54 AM, Carlos Alonso
        <i...@mrcalonso.com
        <mailto:i...@mrcalonso.com><mailto:i...@mrcalonso.com
        <mailto:i...@mrcalonso.com>>> wrote:
        Any update about this?

        @Carlos Rolo, did you tried it? Thoughts?

        Carlos Alonso | Software Engineer |
        @calonso<https://twitter.com/calonso
        <https://twitter.com/calonso>>

        On 5 November 2015 at 14:07, Carlos Rolo <r...@pythian.com
        <mailto:r...@pythian.com><mailto:r...@pythian.com
        <mailto:r...@pythian.com>>> wrote:
        Something to do on a expected rainy weekend. Thanks for the
        information.

        Regards,

        Carlos Juzarte Rolo
        Cassandra Consultant

        Pythian - Love your data

        rolo@pythian | Twitter: @cjrolo | Linkedin:
        linkedin.com/in/carlosjuzarterolo
        
<http://linkedin.com/in/carlosjuzarterolo><http://linkedin.com/in/carlosjuzarterolo
        <http://linkedin.com/in/carlosjuzarterolo>>
        Mobile: +351 91 891 81 00
        <tel:%2B351%2091%20891%2081%2000><tel:%2B351%2091%20891%2081%2000>
        | Tel: +1 613 565 8696 x1649
        
<tel:%2B1%20613%20565%208696%20x1649><tel:%2B1%20613%20565%208696%20x1649>
        www.pythian.com
        <http://www.pythian.com><http://www.pythian.com/
        <http://www.pythian.com/>>

        On Thu, Nov 5, 2015 at 12:07 PM, Dani Traphagen
        <dani.trapha...@datastax.com
        <mailto:dani.trapha...@datastax.com><mailto:dani.trapha...@datastax.com
        <mailto:dani.trapha...@datastax.com>>> wrote:
        As of two days ago, they say they've got it @cjrolo.

        https://github.com/scylladb/scylla/wiki/RELEASE-Scylla-0.11-Beta
        <https://github.com/scylladb/scylla/wiki/RELEASE-Scylla-0.11-Beta>


        On Thursday, November 5, 2015, Carlos Rolo <r...@pythian.com
        <mailto:r...@pythian.com><mailto:r...@pythian.com
        <mailto:r...@pythian.com>>> wrote:
        I will not try until multi-DC is implemented. More than an
        month has passed since I looked for it, so it could possibly
        be in place, if so I may take some time to test it.

        Regards,

        Carlos Juzarte Rolo
        Cassandra Consultant

        Pythian - Love your data

        rolo@pythian | Twitter: @cjrolo | Linkedin:
        linkedin.com/in/carlosjuzarterolo
        
<http://linkedin.com/in/carlosjuzarterolo><http://linkedin.com/in/carlosjuzarterolo
        <http://linkedin.com/in/carlosjuzarterolo>>
        Mobile: +351 91 891 81 00
        <tel:%2B351%2091%20891%2081%2000><tel:%2B351%2091%20891%2081%2000>
        | Tel: +1 613 565 8696 x1649
        
<tel:%2B1%20613%20565%208696%20x1649><tel:%2B1%20613%20565%208696%20x1649>
        www.pythian.com
        <http://www.pythian.com><http://www.pythian.com/
        <http://www.pythian.com/>>

        On Thu, Nov 5, 2015 at 9:37 AM, Jon Haddad
        <jonathan.had...@gmail.com <mailto:jonathan.had...@gmail.com>>
        wrote:
        Nope, no one I know.  Let me know if you try it I'd love to
        hear your feedback.

        > On Nov 5, 2015, at 9:22 AM, tommaso barbugli
        <tbarbu...@gmail.com <mailto:tbarbu...@gmail.com>> wrote:
        >
        > Hi guys,
        >
        > did anyone already try Scylladb (yet another fastest NoSQL
        database in town) and has some thoughts/hands-on experience to
        share?
        >
        > Cheers,
        > Tommaso




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