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Date: Mon, 8 Sep 2003 21:05:00 -0400 (EDT)
From: Jeff Roberson <jroberson@chesapeake.net>
To: Terry Lambert <tlambert2@mindspring.com>
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cc: freebsd-performance@freebsd.org
cc: "Jim C. Nasby" <jim@nasby.net>
Subject: Re: Best disk caching method (and PGSQL performance)
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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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