Re: checkpointer continuous flushing

Hello Andres,

> I measured it in a different number of cases, both on SSDs and spinning
> rust. I just reproduced it with:
>
> postgres-ckpt14 \
>        -D /srv/temp/pgdev-dev-800/ \
>        -c maintenance_work_mem=2GB \
>        -c fsync=on \
>        -c synchronous_commit=off \
>        -c shared_buffers=2GB \
>        -c wal_level=hot_standby \
>        -c max_wal_senders=10 \
>        -c max_wal_size=100GB \
>        -c checkpoint_timeout=30s
>
> Using a fresh cluster each time (copied from a "template" to save time)
> and using
> pgbench -M prepared -c 16 -j 16 -T 300 -P 1

I'm running some tests similar to those above...

Do you do some warmup when testing? I guess the answer is "no".

I understand that you have 8 cores/16 threads on your host?

Loading scale 800 data for 300 seconds tests takes much more than 300 
seconds (init takes ~360 seconds, vacuum & index are slow). With 30 
seconds checkpoint cycles and without any warmup, I feel that these tests 
are really on the very short (too short) side, so I'm not sure how much I 
can trust such results as significant. The data I reported were with more 
real life like parameters.

Anyway, I'll have some results to show with a setting more or less similar 
to yours.

-- 
Fabien.