Re: Major pgbench synthetic SELECT workload regression, Ubuntu 23.04+PG15

On Fri, Jun 9, 2023 at 3:28 AM Gregory Smith <gregsmithpgsql(at)gmail(dot)com> wrote:
> On Thu, Jun 8, 2023 at 9:21 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
>>
>> You might need to add --no-children to the perf report invocation, otherwise
>> it'll show you the call graph inverted.
>
>
> My problem was not writing kernel symbols out, I was only getting addresses for some reason. This worked:
>
> sudo perf record -g --call-graph dwarf -d --phys-data -a sleep 1
> perf report --stdio

Do you know why using phys-data would have solved the problem in your
particular setup? I find figuring out what perf options I need
mystifying.
I end up trying random things from
https://wiki.postgresql.org/wiki/Profiling_with_perf, the perf man
page, and https://www.brendangregg.com/perf.html

The pg wiki page actually has a lot of detail. If you think your
particular problem is something others would encounter, it could be
good to add it there.

FWIW, I think it is helpful to have hackers threads like this where
people work through unexplained performance results with others in the
community.

- Melanie