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  1. ci: macos: Reduce test concurrency

  1. ci: reduce macos test concurrency

    Andres Freund <andres@anarazel.de> — 2022-09-27T04:02:08Z

    Hi,

The x86 mac VMs from cirrus-ci claim to have 12 CPUs, but when working on
initdb caching for tests I noticed that using all those CPUs for tests hurts
the test times noticably.

See [1] (note that the overall time is influenced by different degrees of
cache hit ratios):

concurrency  test time:
4            05:58
6            05:09
8            04:58
10           05:58
12 (current) 06:58

There's a fair bit of run-to-run variance, but the rough shape of these
looks repeatable.

I suspect the VMs might be overcommitted a fair bit - or macos just scales
poorly. Cirrus-ci apparently is switching to M1 based macs, which could be
related. It'd be good for us do that switch, as it'd give use ARM coverage for
CI / cfbot. See also [3].


In 15 (and thus autoconf) the timings differ a bit less [2]:

concurrency  test time:
4            06:54
6            05:43
8            06:09
10           06:01
12 (current) 06:38

Looks like changing TEST_JOBS=6 or 8 would be a good idea.

Greetings,

Andres Freund

[1] https://cirrus-ci.com/build/5254074546257920
[2] https://cirrus-ci.com/task/4888800445857792
[3] https://postgr.es/m/CAN55FZ2R%2BXufuVgJ8ew_yDBk48PgXEBvyKNvnNdTTVyczbQj0g%40mail.gmail.com

  2. Re: ci: reduce macos test concurrency

    Andres Freund <andres@anarazel.de> — 2022-10-02T00:00:08Z

    Hi,

On 2022-09-26 21:02:08 -0700, Andres Freund wrote:
> The x86 mac VMs from cirrus-ci claim to have 12 CPUs, but when working on
> initdb caching for tests I noticed that using all those CPUs for tests hurts
> the test times noticably.
> 
> See [1] (note that the overall time is influenced by different degrees of
> cache hit ratios):
> 
> concurrency  test time:
> 4            05:58
> 6            05:09
> 8            04:58
> 10           05:58
> 12 (current) 06:58
> 
> There's a fair bit of run-to-run variance, but the rough shape of these
> looks repeatable.
> 
> I suspect the VMs might be overcommitted a fair bit - or macos just scales
> poorly. Cirrus-ci apparently is switching to M1 based macs, which could be
> related. It'd be good for us do that switch, as it'd give use ARM coverage for
> CI / cfbot. See also [3].
> 
> 
> In 15 (and thus autoconf) the timings differ a bit less [2]:
> 
> concurrency  test time:
> 4            06:54
> 6            05:43
> 8            06:09
> 10           06:01
> 12 (current) 06:38
> 
> Looks like changing TEST_JOBS=6 or 8 would be a good idea.

Set it to 8 now.

Greetings,

Andres Freund