CPU-bound sysbench on a large server: Postgres 12 to 19 beta1

This has results from sysbench on a small server with Postgres versions 12 through 19 beta1. Sysbench is run with high concurrency (40 connections) and a cached database. The purpose is to search for changes in performance.

Postgres remains boring, it is hard to find performance regressions.

tl;dr for Postgres 17 to 19

• there are no regressions
• throughput on the read-only-count test improves by ~3X in 19 beta1 thanks to a better query plan

tl;dr for Postgres 12 to 19

• there are few regressions, throughput might have dropped by up to 5% on a few range query tests
• there are a few large improvements for read-only tests
• there are many large improvements for write-heavy tests

Builds, configuration and hardware

I compiled Postgres from source for versions 12.22, 13.23, 14.23, 15.18, 16.14, 17.10, 18.4 and 19 beta1.

I used a 48-core server from Hetzner

• an ax162s with an AMD EPYC 9454P 48-Core Processor with SMT disabled
• 2 Intel D7-P5520 NVMe storage devices with RAID 1 (3.8T each) using ext4
• 128G RAM
• Ubuntu 24.04

Configuration files for Postgres:

• the config file is named conf.diff.cx10a_c32r128 (x10a_c32r128) and is here for versions 12, 13, 14, 15, 16 and 17.
• for Postgres 18 and 19 I used conf.diff.cx10b_c32r128 (x10b_c32r128) which is as close as possible to the Postgres 17 config and uses io_method=sync

Benchmark

I used sysbench and my usage is explained here. I now run 32 of the 42 microbenchmarks listed in that blog post. Most test only one type of SQL statement. Benchmarks are run with the database cached by Postgres.

The read-heavy microbenchmarks are run for 600 seconds and the write-heavy for 1200 seconds. The benchmark is run with 40 clients and 8 tables with 10M rows per table. The database is cached.

The purpose is to search for regressions from new CPU overhead and mutex contention. I use the small server with low concurrency to find regressions from new CPU overheads and then larger servers with high concurrency to find regressions from new CPU overheads and mutex contention.

The tests can be called microbenchmarks. They are very synthetic. But microbenchmarks also make it easy to understand which types of SQL statements have great or lousy performance. Performance testing benefits from a variety of workloads -- both more and less synthetic.

Results

The microbenchmarks are split into 4 groups -- 1 for point queries, 2 for range queries, 1 for writes. For the range query microbenchmarks, part 1 has queries that don't do aggregation while part 2 has queries that do aggregation. 

I provide charts below with relative QPS (rQPS). The relative QPS is the following:

(QPS for some version) / (QPS for base version)

When the relative QPS is > 1 then some version is faster than base version.  When it is < 1 then there might be a regression. Values from iostat and vmstat divided by QPS are also provided here. These can help to explain why something is faster or slower because it shows how much HW is used per request.

Here, base version is either Postgres 12.23 or 17.10 and some version is a more recent version. I use 12.23 as the base version to identify regressions over a long period of time. And then I use 17.10 as the base version to confirm there aren't recent, large regressions.

I describe performance changes (changes to relative QPS) in terms of basis points. Performance changes by one basis point when the difference in rQPS is 0.01. When rQPS decreases from 0.95 to 0.85 then it changed by 10 basis points.

Results: point queries, version 17 to 19

Summary:

• there are no regressins

Relative to: PG 17.10

col-1 : PG 18.4

col-2 : PG 19 beta1

col-1   col-2

1.00    0.99    hot-points

1.01    1.01    point-query

1.00    1.00    points-covered-pk

0.98    0.99    points-covered-si

1.01    1.00    points-notcovered-pk

1.00    1.00    points-notcovered-si

1.01    1.01    random-points_range=10

1.02    1.00    random-points_range=100

1.00    1.00    random-points_range=1000

Results: point queries, version 12 to 19

Summary

• there are no regressions
• throughput for the hot-points test improves by ~2X in versions 17.10, 18.4 and 19beta

Relative to: PG 12.22

col-1 : PG 13.23

col-2 : PG 14.23

col-3 : PG 15.18

col-4 : PG 16.14

col-5 : PG 17.10

col-6 : PG 18.4

col-7 : PG 19 beta1

col-1   col-2   col-3   col-4   col-5   col-6   col-7

1.00    0.90    0.97    1.03    2.34    2.35    2.31    hot-points

1.00    1.01    1.03    1.04    1.03    1.04    1.03    point-query

1.02    1.04    1.04    1.07    1.04    1.04    1.04    points-covered-pk

1.01    1.07    1.04    1.04    1.04    1.03    1.04    points-covered-si

0.98    1.01    1.03    1.02    1.00    1.01    1.00    points-notcovered-pk

0.99    1.03    1.03    1.01    1.02    1.02    1.01    points-notcovered-si

0.99    1.01    1.03    1.03    1.00    1.01    1.01    random-points_range=10

0.99    1.02    1.04    1.04    1.01    1.03    1.01    random-points_range=100

1.00    1.02    1.02    1.03    1.01    1.02    1.01    random-points_range=1000

Results: range queries without aggregation, version 17 to 19

Summary

• there are no regressions
• while 19 beta1 has a better result on the scan test, that test has more variance with Postgres so I am reluctant to judge this without more results

Relative to: PG 17.10

col-1 : PG 18.4

col-2 : PG 19 beta1

col-1   col-2

0.98    0.99    range-covered-pk

0.97    0.99    range-covered-si

0.99    0.99    range-notcovered-pk

1.02    1.01    range-notcovered-si

0.96    1.07    scan

Results: range queries without aggregation, version 12 to 19

Summary

• there are no regressions
• scan throughput has improved a lot from version 12 to 19

Relative to: PG 12.22

col-1 : PG 13.23

col-2 : PG 14.23

col-3 : PG 15.18

col-4 : PG 16.14

col-5 : PG 17.10

col-6 : PG 18.4

col-7 : PG 19 beta1

col-1   col-2   col-3   col-4   col-5   col-6   col-7

0.99    1.03    1.04    1.04    1.03    1.00    1.02    range-covered-pk

0.99    1.04    1.04    1.04    1.03    1.00    1.03    range-covered-si

1.00    1.00    1.00    0.99    1.00    0.99    0.99    range-notcovered-pk

1.00    1.01    1.01    0.99    1.00    1.02    1.01    range-notcovered-si

1.09    1.27    1.10    1.21    1.19    1.14    1.28    scan

Results: range queries with aggregation, version 17 to 19

Summary

• there are no regressions
• throughput on the read-only-count test is ~3X better thanks to a new query plan. This improvement was also visible on my small server

Relative to: PG 17.10

col-1 : PG 18.4

col-2 : PG 19 beta1

col-1   col-2

1.03    3.30    read-only-count

1.02    0.99    read-only-distinct

1.00    0.97    read-only-order

0.99    0.99    read-only_range=10

0.99    0.99    read-only_range=100

1.01    1.00    read-only_range=10000

1.03    1.01    read-only-simple

1.03    1.01    read-only-sum

Results: range queries with aggregation, version 12 to 19

Summary

• there might be a few small regressions, but losing 5% throughput from version 12 to 19 isn't a big deal
• throughput on the read-only-count test is ~3X better thanks to a new query plan. This improvement was also visible on my small server

Relative to: PG 12.22

col-1 : PG 13.23

col-2 : PG 14.23

col-3 : PG 15.18

col-4 : PG 16.14

col-5 : PG 17.10

col-6 : PG 18.4

col-7 : PG 19 beta1

col-1   col-2   col-3   col-4   col-5   col-6   col-7

1.01    0.95    0.96    0.97    0.93    0.95    3.06    read-only-count

1.00    0.98    0.98    0.98    0.96    0.98    0.95    read-only-distinct

1.00    0.98    0.98    1.00    0.99    0.99    0.97    read-only-order

0.99    1.00    1.01    1.00    1.01    0.99    1.00    read-only_range=10

0.99    1.00    1.00    1.00    1.01    1.00    0.99    read-only_range=100

1.00    0.97    1.02    1.03    1.04    1.05    1.03    read-only_range=10000

1.00    0.97    0.99    0.97    0.95    0.98    0.96    read-only-simple

1.00    0.96    0.97    0.97    0.94    0.97    0.95    read-only-sum

Results: writes, version 17 to 19

Summary

• there are no regressions

Relative to: PG 17.10

col-1 : PG 18.4

col-2 : PG 19 beta1

col-1   col-2

0.99    0.99    delete

1.02    1.02    insert

1.00    0.98    read-write_range=10

0.99    0.99    read-write_range=100

1.01    1.03    update-index

1.01    0.98    update-inlist

0.98    1.01    update-nonindex

1.01    1.03    update-one

1.00    1.00    update-zipf

0.97    0.99    write-only

Results: writes, version 12 to 19

Summary

• there are no regressions
• many large improvements arrived in version 17 and remain in 19 beta1

Relative to: PG 12.22

col-1 : PG 13.23

col-2 : PG 14.23

col-3 : PG 15.18

col-4 : PG 16.14

col-5 : PG 17.10

col-6 : PG 18.4

col-7 : PG 19 beta1

col-1   col-2   col-3   col-4   col-5   col-6   col-7

0.99    1.11    1.13    1.10    1.28    1.27    1.27    delete

1.02    1.17    1.16    1.19    1.23    1.25    1.25    insert

1.00    1.20    1.22    1.20    1.24    1.24    1.22    read-write_range=10

0.99    1.04    1.05    1.04    1.06    1.05    1.04    read-write_range=100

0.98    1.08    1.05    0.94    1.84    1.85    1.90    update-index

1.00    1.07    1.06    1.05    1.12    1.13    1.10    update-inlist

1.01    1.07    1.07    0.86    1.87    1.84    1.88    update-nonindex

1.04    0.96    0.96    1.10    1.39    1.41    1.43    update-one

1.01    1.05    1.07    0.96    1.63    1.62    1.63    update-zipf

0.99    1.11    1.13    1.09    1.41    1.37    1.40    write-only