| From: | Tomas Vondra <tomas(at)vondra(dot)me> |
|---|---|
| To: | Achilleas Mantzios - cloud <a(dot)mantzios(at)cloud(dot)gatewaynet(dot)com>, pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: tds_fdw : Severe performance degradation from postgresql 10.23 to 16.4 |
| Date: | 2024-11-12 13:17:53 |
| Message-ID: | 14f7d64f-d864-4429-9cf2-7ef92d6a90fb@vondra.me |
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| Lists: | pgsql-performance |
On 11/12/24 11:37, Achilleas Mantzios - cloud wrote:
>
> ...
>
> We run perf on both systems for 90 seconds to make sure that it included
> at least two runs of the slow system, and we attach both outputs. We run
> perf as :
>
> sudo perf record -g -p <PID> -- sleep 90
>
> it strikes me that we dont find similarities between the two, but we are
> new to perf.
>
Not sure, but it seems the slow profile has a lot of writes. Not sure
why. Do both instances have the same work_mem value / available memory,
storatge?
Maybe EXPLAIN VERBOSE would show if the remote query is the same ...
Maybe try setting log_temp_files=0 before running the query. Writing the
foreign scan result set into a temp file could be happening on one of
the machines only.
regards
--
Tomas Vondra
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