Re: POC: Cache data in GetSnapshotData()

Thanks Amit,
I did a quick pgbench write tests for unlogged tables at 88 clients as it
had the peak performance from previous test. There is big jump in TPS due
to clog changes.

clients BASE ONLY CLOG CHANGES % Increase ONLY SAVE SNAPSHOT % Increase CLOG
CHANGES + SAVE SNAPSHOT % Increase
88 36055.425005 52796.618434 46.4318294034 37728.004118 4.6389111008
56025.454917 55.3870323515
Clients + WITH INCREASE IN CLOG BUFFER % increase
88 58217.924138 61.4678626862

I will continue to benchmark above tests with much wider range of clients.

On Thu, Mar 10, 2016 at 1:36 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:

> On Thu, Mar 10, 2016 at 1:04 PM, Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com>
> wrote:
>
>>
>>
>> On Thu, Mar 3, 2016 at 11:50 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
>> wrote:
>> >What if you apply both this and Amit's clog control log patch(es)?
>> Maybe the combination of the two helps substantially more than either >one
>> alone.
>>
>>
>> I did the above tests along with Amit's clog patch. Machine :8 socket, 64
>> core. 128 hyperthread.
>>
>> clients BASE ONLY CLOG CHANGES % Increase ONLY SAVE SNAPSHOT % Increase CLOG
>> CHANGES + SAVE SNAPSHOT % Increase
>> 64 29247.658034 30855.728835 5.4981181711 29254.532186 0.0235032562
>> 32691.832776 11.7758992463
>> 88 31214.305391 33313.393095 6.7247618606 32109.248609 2.8670931702
>> 35433.655203 13.5173592978
>> 128 30896.673949 34015.362152 10.0939285832 *** *** 34947.296355
>> 13.110221549
>> 256 27183.780921 31192.895437 14.7481857938 *** *** 32873.782735
>> 20.9316056164
>> With clog changes, perf of caching the snapshot patch improves.
>>
>>
> This data looks promising to me and indicates that saving the snapshot has
> benefits and we can see noticeable performance improvement especially once
> the CLog contention gets reduced. I wonder if we should try these tests
> with unlogged tables, because I suspect most of the contention after
> CLogControlLock and ProcArrayLock is for WAL related locks, so you might be
> able to see better gain with these patches. Do you think it makes sense to
> check the performance by increasing CLOG buffers (patch for same is posted
> in Speed up Clog thread [1]) as that also relieves contention on CLOG as
> per the tests I have done?
>
>
> [1] -
> http://www.postgresql.org/message-id/CAA4eK1LMMGNQ439BUm0LcS3p0sb8S9kc-cUGU_ThNqMwA8_Tug@mail.gmail.com
>
> With Regards,
> Amit Kapila.
> EnterpriseDB: http://www.enterprisedb.com
>

--
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com