Re: test_fsync open_sync test

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: test_fsync open_sync test
Date: 2011-01-18 16:44:57
Message-ID: 201101181644.p0IGiv508938@momjian.us
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Greg Smith wrote:
> Bruce Momjian wrote:
> > Is there a value to this test_fsync test?
> >
> > Compare open_sync with different sizes:
> > (This is designed to compare the cost of one large
> > sync'ed write and two smaller sync'ed writes.)
> > open_sync 16k write 242.563 ops/sec
> > 2 open_sync 8k writes 752.752 ops/sec
> >
> > It compares the cost of doing larger vs. two smaller open_sync writes.
> >
>
> Might be some value for determining things like what the optimal WAL
> block size to use is. All these tests are kind of hard to use
> effectively still, I'm not sure if it's time to start trimming tests yet
> until we've made more progress on interpreting results first.

OK, thanks for the feedback. I just wanted to make sure it wasn't a
stupid test.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +

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