Re: checkpointer continuous flushing - V18

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: checkpointer continuous flushing - V18
Date: 2016-02-22 13:11:05
Message-ID: alpine.DEB.2.10.1602221402570.19971@sto
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> I did a quick & small test with random updates on 16 tables with
> checkpoint_flush_after=16 checkpoint_timeout=30

Another run with more "normal" settings and over 1000 seconds, so less
"quick & small" that the previous one.

checkpoint_flush_after = 16
checkpoint_timeout = 5min # default
shared_buffers = 2GB # 1/8 of available memory

Random updates on 16 tables which total to 1.1GB of data, so this is in
buffer, no significant "read" traffic.

(1) with 16 tablespaces (1 per table) on 1 disk : 680.0 tps
per second avg, stddev [ min q1 median d3 max ] <=300tps
679.6 ± 750.4 [0.0, 317.0, 371.0, 438.5, 2724.0] 19.5%

(2) with 1 tablespace on 1 disk : 956.0 tps
per second avg, stddev [ min q1 median d3 max ] <=300tps
956.2 ± 796.5 [3.0, 488.0, 583.0, 742.0, 2774.0] 2.1%

--
Fabien.

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