Re: Performance degradation in commit ac1d794

2015-12-25 20:27 GMT+03:00 Васильев Дмитрий <d(dot)vasilyev(at)postgrespro(dot)ru>:

>
> 2015-12-25 20:18 GMT+03:00 Andres Freund <andres(at)anarazel(dot)de>:
>
>> On December 25, 2015 6:08:15 PM GMT+01:00, "Васильев Дмитрий" <
>> d(dot)vasilyev(at)postgrespro(dot)ru> wrote:
>> >Hello hackers!
>> >
>> >I suddenly found commit ac1d794 gives up to 3 times performance
>> >degradation.
>> >
>> >I tried to run pgbench -s 1000 -j 48 -c 48 -S -M prepared on 70
>> >CPU-core
>> >machine:
>> >commit ac1d794 gives me 363,474 tps
>> >and previous commit a05dc4d gives me 956,146
>> >and master( 3d0c50f ) with revert ac1d794 gives me 969,265
>> >
>> >it's shocking
>>
>>
>>
>> ​
>> You're talking about
>> http://git.postgresql.org/gitweb/?p=postgresql.git;a=blobdiff;f=src/backend/libpq/be-secure.c;h=2ddcf428f89fd12c230d6f417c2f707fbd97bf39;hp=26d8faaf773a818b388b899b8d83d617bdf7af9b;hb=ac1d794;hpb=a05dc4d7fd57d4ae084c1f0801973e5c1a1aa26e
>>
>> ​​
>> If so, could you provide a hierarchical before/after profile?
>>
>> Andres
>> Hi,
>>
>> ---
>> Please excuse brevity and formatting - I am writing this on my mobile
>> phone.
>>
>
> ​> ​You're talking about
> http://git.postgresql.org/gitweb/?p=postgresql.git;a=blobdiff;f=src/backend/libpq/be-secure.c;h=2ddcf428f89fd12c230d6f417c2f707fbd97bf39;hp=26d8faaf773a818b388b899b8d83d617bdf7af9b;hb=ac1d794;hpb=a05dc4d7fd57d4ae084c1f0801973e5c1a1aa26e
>
> Yes, about this.
>
> >​If so, could you provide a hierarchical before/after profile?
>
> ​Performance | Git hash commit | Date
> ~ 360k tps | c3e7c24a1d60dc6ad56e2a0723399f1570c54224 | Thu Nov 12
> 09:12:18 2015 -0500
> ~ 360k tps | ac1d7945f866b1928c2554c0f80fd52d7f977772 | Thu Nov 12
> 09:00:33 2015 -0500
> ~ 960k tps | a05dc4d7fd57d4ae084c1f0801973e5c1a1aa26e | Thu Nov 12
> 07:40:31 2015 -0500
>
>
> ​​
> ​​---
> Dmitry Vasilyev
> Postgres Professional: http://www.postgrespro.com
> Russian Postgres Company​
>
>
​I came across it by studying the results:​​

vanilla 9.5 = 30020c3fc3b6de5592978313df929d370f5770ce
vanilla 9.6 = c4a8812cf64b142685e39a69694c5276601f40e4

​
info | clients | tps
-----------------------+---------+---------
vanilla 9.5 | 1 | 30321
vanilla 9.5 | 8 | 216542
vanilla 9.5 | 16 | 412526
vanilla 9.5 | 32 | 751331
vanilla 9.5 | 48 | 956146
​ <- this point​
vanilla 9.5 | 56 | 990122
vanilla 9.5 | 64 | 842436
vanilla 9.5 | 72 | 913272
vanilla 9.5 | 82 | 659332
vanilla 9.5 | 92 | 630111
vanilla 9.5 | 96 | 616863
vanilla 9.5 | 110 | 592080
vanilla 9.5 | 120 | 575831
vanilla 9.5 | 130 | 557521
vanilla 9.5 | 140 | 537951
vanilla 9.5 | 150 | 517019
vanilla 9.5 | 160 | 502312
vanilla 9.5 | 170 | 489162
vanilla 9.5 | 180 | 477178
vanilla 9.5 | 190 | 464620
vanilla 9.6 | 1 | 31738
vanilla 9.6 | 8 | 219692
vanilla 9.6 | 16 | 422933
vanilla 9.6 | 32 | 375546
vanilla 9.6 | 48 | 363474
​ <- this point​
vanilla 9.6 | 56 | 352943
vanilla 9.6 | 64 | 334498
vanilla 9.6 | 72 | 369802
vanilla 9.6 | 82 | 604867
vanilla 9.6 | 92 | 871048
vanilla 9.6 | 96 | 969265
vanilla 9.6 | 105 | 996794
vanilla 9.6 | 110 | 932853
vanilla 9.6 | 115 | 758485
vanilla 9.6 | 120 | 721365
vanilla 9.6 | 125 | 632265
vanilla 9.6 | 130 | 624666
vanilla 9.6 | 135 | 582120
vanilla 9.6 | 140 | 583080
vanilla 9.6 | 150 | 555608
vanilla 9.6 | 160 | 533340
vanilla 9.6 | 170 | 520308
vanilla 9.6 | 180 | 504536
vanilla 9.6 | 190 | 496967​

​​​​---
Dmitry Vasilyev
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company​​