svn commit: r193878 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

[John Baldwin]

On Wednesday 10 June 2009 6:02:12 am Dag-Erling Smørgrav wrote:
> Kip Macy <kmacy at freebsd.org> writes:
> > Dmitry Morozovsky <marck at rinet.ru> writes:
> > > Hmm, I failed to see how boolean prevent the usage:
> > >
> > > if arch==i386 || memsize < 4G
> > >        zfs_prefetch=0
> > > else
> > >        zfs_prefetch=1
> > >
> > > and admin can flip the switch to non-default position.
> > >
> > Right, what you're advocating is zfs_prefetch_non_default. Which is
> > simpler, but still rather weird.
> 
> No, he's advocating zfs_prefetch_enable which is initialized to either 0
> or 1 at boot time and can be administratively set to either 0 and 1
> regardless of its initial value.  I don't see the problem...

Yes, you can simply do a TUNABLE_INT_FETCH() after the initial calculation to 
honor any user override.  Many existing settings already work this way where 
the user can override the auto-tuned value (e.g. all the buffer-cache tuning 
settings).

-- 
John Baldwin