Re: Sysbench tests on PG12

On Fri, 2021-10-01 at 14:22 +0530, Subhrajyoti Senapati wrote:
> Was running a few sysbench tests in Postgres12.
> Sysbench Test Config
> oltp-readwrite-custom
> Threads - 500
> Machine: 16 core 64G
>
> In PG server:
> shared_buffers: 16GB
> maintenance_work_memory: 16GB
> checkpoint_timeout: 1h
> max_wal_size: 10GB
> wal_sync_method: 'open_sync'
> effective_cache_size: 32GB
> wal_buffers: -1
> wal_compression: on
>
> Got some qps dips.
>
> Changed fsync and full_page_rewrite to 'off'.
> Which helped in avoiding these many long dips in performance:
>
> But fsync ensures DBMS consistency. So, instead of that can I change a few other configurations to avoid these inconsistent performance dips ?

Try playing with "bgwriter_flush_after", "checkpoint_flush_after" and "wal_writer_flush_after"
and see if that influences the behavior.

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com