From: Reza Taheri <rtaheri@vmware.com>
To: Ryan Johnson <ryan.johnson@cs.utoronto.ca>
CC: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: High rate of transaction failure with the Serializable
 Isolation Level
Thread-Topic: High rate of transaction failure with the Serializable
 Isolation Level
Thread-Index: AQHPqFHVx3JypHx58U+0ZXroXUnibJuyxa9ggACJy4D//6OtMA==
Date: Sat, 26 Jul 2014 23:33:10 +0000
Message-ID: <a34f6676d65949f19c5efad75cbefe2f@EX13-MBX-013.vmware.com>
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Hi Ryan,
Thanks a lot for sharing this. When I run with 12 CE threads and 3-5 MEE th=
reads (how many MEE threads do you have?) @  80-90 tps, I get something in =
the 20-30% of trade-result transactions rolled back depending on how I coun=
t. E.g., in a 5.5-minute run with 3 MEE threads, I saw 87.5 tps. There were=
 29200 successful trade-result transactions. Of these, 5800 were rolled bac=
k, some more than once for a total of 8450 rollbacks. So I'd say your resul=
ts and ours tell similar stories!

Thanks,
Reza

> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org [mailto:pgsql-
> performance-owner@postgresql.org] On Behalf Of Ryan Johnson
> Sent: Saturday, July 26, 2014 2:06 PM
> To: Reza Taheri
> Cc: pgsql-performance@postgresql.org
> Subject: Re: High rate of transaction failure with the Serializable Isola=
tion
> Level
>=20
> Dredging through some old run logs, 12 dbt-5 clients gave the following w=
hen
> everything was run under SSI (fully serializable, even the transactions t=
hat
> allow repeatable read isolation). Not sure how that translates to your re=
sults.
> Abort rates were admittedly rather high, though perhaps lower than what
> you report.
>=20
> Transaction             % Average: 90th %   Total Rollbacks    % Warning =
Invalid
> ----------------- ------- --------------- ------- -------------- ------- =
-------
> Trade Result        5.568   0.022:  0.056    2118    417  19.69%       0 =
     91
> Broker Volume       5.097   0.009:  0.014    1557      0   0.00%       0 =
      0
> Customer Position  13.530   0.016:  0.034    4134      1   0.02%       0 =
      0
> Market Feed         0.547   0.033:  0.065     212     45  21.23%       0 =
     69
> Market Watch       18.604   0.031:  0.061    5683      0   0.00%       0 =
      0
> Security Detail    14.462   0.015:  0.020    4418      0   0.00%       0 =
      0
> Trade Lookup        8.325   0.059:  0.146    2543      0   0.00%     432 =
      0
> Trade Order         9.110   0.006:  0.008    3227    444  13.76%       0 =
      0
> Trade Status       19.795   0.030:  0.046    6047      0   0.00%       0 =
      0
> Trade Update        1.990   0.064:  0.145     608      0   0.00%     432 =
      0
> Data Maintenance      N/A   0.012:  0.012       1      0   0.00%       0 =
      0
> ----------------- ------- --------------- ------- -------------- ------- =
-------
> 28.35 trade-result transactions per second (trtps)
>=20
> Regards,
> Ryan
>=20
> On 26/07/2014 3:55 PM, Reza Taheri wrote:
> > Hi Ryan,
> > That's a very good point. We are looking at dbt5. One question: what
> throughput rate, and how many threads of execution did you use for dbt5?
> The failure rates I reported were at ~120 tps with 15 trade-result thread=
s.
> >
> > Thanks,
> > Reza
> >
> >> -----Original Message-----
> >> From: pgsql-performance-owner@postgresql.org [mailto:pgsql-
> >> performance-owner@postgresql.org] On Behalf Of Ryan Johnson
> >> Sent: Friday, July 25, 2014 2:36 PM
> >> To: pgsql-performance@postgresql.org
> >> Subject: Re: High rate of transaction failure with the Serializable
> >> Isolation Level
> >>
> >> On 25/07/2014 2:58 PM, Reza Taheri wrote:
> >>> Hi Craig,
> >>>
> >>>> According to the attached SQL, each frame is a separate phase in
> >>>> the
> >> operation and performs many different operations.
> >>>> There's a *lot* going on here, so identifying possible
> >>>> interdependencies isn't something I can do in a ten minute skim
> >>>> read over
> >> my morning coffee.
> >>> You didn't think I was going to bug you all with a trivial problem,
> >>> did you? :-) :-)
> >>>
> >>> Yes, I am going to have to take an axe to the code and see what pops
> out.
> >> Just to put this in perspective, the transaction flow and its
> >> statements are borrowed verbatim from the TPC-E benchmark. There
> have
> >> been dozens of TPC-E disclosures with MS SQL Server, and there are
> >> Oracle and DB2 kits that, although not used in public disclosures for
> >> various non-technical reasons, are used internally in by the DB and
> >> server companies. These 3 products, and perhaps more, were used
> extensively in the prototyping phase of TPC-E.
> >>> So, my hope is that if there is a "previously unidentified
> >>> interdependency
> >> between transactions" as you point out, it will be due to a mistake
> >> we made in coding this for PGSQL. Otherwise, we will have a hard time
> >> convincing all the council member companies that we need to change
> >> the schema or the business logic to make the kit work with PGSQL.
> >>> Just pointing out my uphill battle!!
> >> You might compare against dbt-5 [1], just to see if the same problem
> >> occurs. I didn't notice such high abort rates when I ran that
> >> workload a few weeks ago. Just make sure to use the latest commit,
> >> because the "released" version has fatal bugs.
> >>
> >> [1]
> >>
> https://urldefense.proofpoint.com/v1/url?u=3Dhttps://github.com/peterge
> >> og
> hegan/dbt5&k=3DoIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=3Db9TKmA0CPjr
> >>
> oD2HLPTHU27nI9PJr8wgKO2rU9QZyZZU%3D%0A&m=3D6E%2F9fWJPMGjpMyP
> >>
> xtY0nsamLLW%2FNsTXu7FP9Wzauj10%3D%0A&s=3Db3f269216d419410f3f07bb
> >> 774a27b7d377744c9d423df52a3e62324d9279958
> >>
> >> Ryan
> >>
> >>
> >>
> >> --
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> performance&k=3DoIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=3Db9TKmA0CP
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>=20
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