From: Tomas Vondra <tv@fuzzy.cz>
To: pgsql-performance@postgresql.org
Subject: Re: how to demonstrate the effect of direct I/O ?
Date: Sun, 05 Feb 2012 00:34:23 +0100
Message-ID: <4F2DC07F.1080902@fuzzy.cz> (raw)
In-Reply-To: <4F2DBE5A.9090102@fuzzy.cz>
References: <4F2DBE5A.9090102@fuzzy.cz>
On 5.2.2012 00:25, Tomas Vondra wrote:
> Hi all,
>
> I've been running a lot of benchmarks recently (I'll publish the results
> once I properly analyze them). One thing I'd like to demonstrate is the
> effect of direct I/O when the wal_fsync_method is set to
> open_sync/open_datasync.
>
> I.e. I'd like to see cases when this improves/hurts performance
> (compared to fsync/fdatasync) and if/how this works on SSD compared to
> old-fashioned HDD. But no matter what, I see no significant differences
> in performance.
BTW the benchmark suite I run consists of two parts:
(a) read-write pgbench
(b) TPC-H-like benchmark that loads a few GBs of data (and then
queries them)
I'd expect to see the effect on the TPC-H load part, and maybe on the
pgbench (not sure if positive or negative).
> All this was run on a kernel 3.1.5 using an ext4 filesystem.
And the Pg versions tested were 9.1.2 and the current 9.2dev snapshot.
Tomas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz
Subject: Re: how to demonstrate the effect of direct I/O ?
In-Reply-To: <4F2DC07F.1080902@fuzzy.cz>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox