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Re: [PERFORM] Direct I/O issues

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Greg Smith <gsmith(at)gregsmith(dot)com>
Cc: PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: [PERFORM] Direct I/O issues
Date: 2006-11-24 18:58:45
Message-ID: 200611241858.kAOIwjh23094@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patchespgsql-performance
Greg Smith wrote:
> On Thu, 23 Nov 2006, Tom Lane wrote:
> 
> > * It does not check for errors (if it had, you might have realized the
> >  other problem).
> 
> All the test_fsync code needs to check for errors better; there have been 
> multiple occasions where I've run that with quesiontable input and it 
> didn't complain, it just happily ran and reported times that were almost 
> 0.
> 
> Thanks for the note about alignment, I had seen something about that in 
> the xlog.c but wasn't sure if that was important in this case.
> 
> It's very important to the project I'm working on that I get this cleared 
> up, and I think I'm in a good position to fix it myself now.  I just 
> wanted to report the issue and get some initial feedback on what's wrong. 
> I'll try to rewrite that code with an eye toward the "Determine optimal 
> fdatasync/fsync, O_SYNC/O_DSYNC options" to-do item, which is what I'd 
> really like to have.

I have developed a patch that moves the defines into a include file
where they can be used by the backend and test_fsync.c.  I have also set
up things so there is proper alignment for O_DIRECT, and added error
checking.

Not sure if people want this for 8.2.  I think we can modify
test_fsync.c anytime but the movement of the defines into an include
file is a backend code change.

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

  + If your life is a hard drive, Christ can be your backup. +

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Description: text/x-diff (16.9 KB)

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