Best disk caching method (and PGSQL performance)

[Jeff Roberson]

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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