Perf Benchmarking and regression.

I tried to do some benchmarking on postgres master head
commit 72a98a639574d2e25ed94652848555900c81a799
Author: Andres Freund <andres(at)anarazel(dot)de>
Date: Tue Apr 26 20:32:51 2016 -0700

CASE : Read-Write Tests when data exceeds shared buffers.

Non Default settings and test
./postgres -c shared_buffers=8GB -N 200 -c min_wal_size=15GB -c
max_wal_size=20GB -c checkpoint_timeout=900 -c maintenance_work_mem=1GB -c
checkpoint_completion_target=0.9 &

./pgbench -i -s 1000 postgres

./pgbench -c $threads -j $threads -T 1800 -M prepared postgres

Machine : "cthulhu" 8 node numa machine with 128 hyper threads.
>numactl --hardware
available: 8 nodes (0-7)
node 0 cpus: 0 65 66 67 68 69 70 71 96 97 98 99 100 101 102 103
node 0 size: 65498 MB
node 0 free: 37885 MB
node 1 cpus: 72 73 74 75 76 77 78 79 104 105 106 107 108 109 110 111
node 1 size: 65536 MB
node 1 free: 31215 MB
node 2 cpus: 80 81 82 83 84 85 86 87 112 113 114 115 116 117 118 119
node 2 size: 65536 MB
node 2 free: 15331 MB
node 3 cpus: 88 89 90 91 92 93 94 95 120 121 122 123 124 125 126 127
node 3 size: 65536 MB
node 3 free: 36774 MB
node 4 cpus: 1 2 3 4 5 6 7 8 33 34 35 36 37 38 39 40
node 4 size: 65536 MB
node 4 free: 62 MB
node 5 cpus: 9 10 11 12 13 14 15 16 41 42 43 44 45 46 47 48
node 5 size: 65536 MB
node 5 free: 9653 MB
node 6 cpus: 17 18 19 20 21 22 23 24 49 50 51 52 53 54 55 56
node 6 size: 65536 MB
node 6 free: 50209 MB
node 7 cpus: 25 26 27 28 29 30 31 32 57 58 59 60 61 62 63 64
node 7 size: 65536 MB
node 7 free: 43966 MB
node distances:
node 0 1 2 3 4 5 6 7
0: 10 21 21 21 21 21 21 21
1: 21 10 21 21 21 21 21 21
2: 21 21 10 21 21 21 21 21
3: 21 21 21 10 21 21 21 21
4: 21 21 21 21 10 21 21 21
5: 21 21 21 21 21 10 21 21
6: 21 21 21 21 21 21 10 21
7: 21 21 21 21 21 21 21 10

I see some regression when compared to 9.5

*Sessions* *PostgreSQL-9.5 scale 1000* *PostgreSQL-9.6 scale 1000* %diff
*1* 747.367249 892.149891 19.3723557185
*8* 5281.282799 4941.905008 -6.4260484416
*16* 9000.915419 8695.396233 -3.3943123758
*24* 11852.839627 10843.328776 -8.5170379653
*32* 14323.048334 11977.505153 -16.3760054864
*40* 16098.926583 12195.447024 -24.2468312336
*48* 16959.646965 12639.951087 -25.4704351271
*56* 17157.737762 12543.212929 -26.894715941
*64* 17201.914922 12628.002422 -26.5895542487
*72* 16956.994835 11280.870599 -33.4736448954
*80* 16775.954896 11348.830603 -32.3506132834
*88* 16609.137558 10823.465121 -34.834273705
*96* 16510.099404 11091.757753 -32.8183466278
*104* 16275.724927 10665.743275 -34.4683980416
*112* 16141.815128 10977.84664 -31.9912503461
*120* 15904.086614 10716.17755 -32.6199749153
*128* 15738.391503 10962.333439 -30.3465450271

When I run git bisect on master (And this is for 128 clients).

2 commitIds which affected the performance

1. # first bad commit: [ac1d7945f866b1928c2554c0f80fd52d7f977772] Make idle
backends exit if the postmaster dies.
this made performance to drop from

15947.21546 (15K +) to 13409.758510 (arround 13K+).

2. # first bad commit: [428b1d6b29ca599c5700d4bc4f4ce4c5880369bf] Allow to
trigger kernel writeback after a configurable number of writes.

this made performance to drop further to 10962.333439 (10K +)

I think It did not recover afterwards.
--
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com