To: "fkater\@googlemail.com" <fkater@googlemail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Inserting 8MB bytea: just 25% of disk perf used?
References: <20100114142903.GB2973@comppasch2> <82aawgoh09.fsf@mid.bfk.de>
	<20100114212719.GE2384@comppasch2>
From: Florian Weimer <fweimer@bfk.de>
Date: Fri, 15 Jan 2010 08:02:49 +0000
In-Reply-To: <20100114212719.GE2384@comppasch2> (fkater@googlemail.com's
	message of "Thu\, 14 Jan 2010 22\:27\:19 +0100")
Message-ID: <82hbqnkd7a.fsf@mid.bfk.de>
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> Florian Weimer:
>
>> > Do you have any further idea why 16MB/s seems to be the limit here?
>>=20
>> BYTEA deserialization is very slow, and this could be a factor here.
>> Have you checked that you are in fact I/O bound?
>
> Could you elaborate that a bit? It sounds interesting but I
> do not get what you mean by:
>
> "bytea deserialization": Do you mean from an escaped string
> back to real binary data?

Yes, that is what I meant.

> Does that apply to my case (I use PGexecParam and have the Format
> arg set to 1, binary) ?

Yes, this was my suggestion.  There is probably some other issue,
then.

> "I/O bound": What do you mean by that?

You should check (presumably using the Windows performance monitoring
tools, but I'm not familiar with Windows) if the PostgreSQL process is
indeed waiting on disk I/O.

--=20
Florian Weimer                <fweimer@bfk.de>
BFK edv-consulting GmbH       http://www.bfk.de/
Kriegsstra=DFe 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99