Last I remember, we were going to add this as an option. But I don't
see a patch in the queue. Am I missing it? Was I supposed to write it?

--
-- Josh Berkus
PostgreSQL Experts Inc.
http://www.pgexperts.com

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  • Bruce Momjian at Jan 16, 2011 at 12:30 am

    Josh Berkus wrote:
    Last I remember, we were going to add this as an option. But I don't
    see a patch in the queue. Am I missing it? Was I supposed to write it?
    I don't know, but let me add that I am confused how this would look to
    users. In many cases, kernels don't even support O_DIRECT, so what
    would we do to specify this? What about just auto-disabling O_DIRECT if
    the filesystem does not support it; maybe issue a log message about it.

    --
    Bruce Momjian <bruce@momjian.us> http://momjian.us
    EnterpriseDB http://enterprisedb.com

    + It's impossible for everything to be true. +
  • Josh Berkus at Jan 16, 2011 at 8:12 pm

    On 1/15/11 4:30 PM, Bruce Momjian wrote:
    Josh Berkus wrote:
    Last I remember, we were going to add this as an option. But I don't
    see a patch in the queue. Am I missing it? Was I supposed to write it?
    I don't know, but let me add that I am confused how this would look to
    users. In many cases, kernels don't even support O_DIRECT, so what
    would we do to specify this? What about just auto-disabling O_DIRECT if
    the filesystem does not support it; maybe issue a log message about it.
    Yes, you *are* confused. The problem isn't auto-disabling, we already
    do that. The problem is *auto-enabling*; ages ago we made the
    assumption that if o_sync was supported, so was o_direct. We've now
    found out that's not true on all platforms.

    Also, test results show that even when supported, o_direct isn't
    necessarily a win. Hence, the additional fsync_method options.

    --
    -- Josh Berkus
    PostgreSQL Experts Inc.
    http://www.pgexperts.com
  • Bruce Momjian at Jan 17, 2011 at 6:08 pm

    Josh Berkus wrote:
    On 1/15/11 4:30 PM, Bruce Momjian wrote:
    Josh Berkus wrote:
    Last I remember, we were going to add this as an option. But I don't
    see a patch in the queue. Am I missing it? Was I supposed to write it?
    I don't know, but let me add that I am confused how this would look to
    users. In many cases, kernels don't even support O_DIRECT, so what
    would we do to specify this? What about just auto-disabling O_DIRECT if
    the filesystem does not support it; maybe issue a log message about it.
    Yes, you *are* confused. The problem isn't auto-disabling, we already
    do that. The problem is *auto-enabling*; ages ago we made the
    assumption that if o_sync was supported, so was o_direct. We've now
    found out that's not true on all platforms.

    Also, test results show that even when supported, o_direct isn't
    necessarily a win. Hence, the additional fsync_method options.
    I think it would be clear if we did not use o_direct for open_*sync, but
    only for open_*sync_direct, so there was no auto-direct anything --- you
    had to ask for it, and if we don't support it, you get an error. Right
    now people aren't sure what they are getting.

    --
    Bruce Momjian <bruce@momjian.us> http://momjian.us
    EnterpriseDB http://enterprisedb.com

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

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postedJan 15, '11 at 10:16p
activeJan 17, '11 at 6:08p
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