Re: Best disk caching method (and PGSQL performance)

From: Jeff Roberson (jroberson_at_chesapeake.net)
Date: 09/09/03

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    Date: Mon, 8 Sep 2003 21:05:00 -0400 (EDT)
To: Terry Lambert <tlambert2@mindspring.com>

    On Fri, 5 Sep 2003, Terry Lambert wrote:

    > Sean Chittenden wrote:
    > > > Also, has anyone played with the other fsync options?
    > >
    > > FreeBSD only supports the default fsync option.
    >
    > And as the comments point out, it lacks the introspection to
    > know dirty pages from clean ones, so all pages that are in
    > core and associated with the object are written, not just
    > the dirty ones. Avoid this, if possible.

    This is not accurate at all. Please see vfs_subr.c's vop_stdfsync(). We
    walk the dirty block head and flush those buffers that are dirty.

    >
    > It would be nice if there were an fcntl that would F_SYNCRANGE
    > or something similar, so the applicaion could hint the range it
    > wanted written to the kernel.
    >
    > -- Terry
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