setting tunables in stable/10 vs head?

[Ian Lepore]

On Wed, 2015-06-10 at 20:44 -0700, hiren panchasara wrote:
> On 06/10/15 at 04:13P, Rick Macklem wrote:
> > Hi,
> > 
> > I just MFC'd a patch from head to stable/10 that defines some
> > tunables using CTLFLAG_RDTUN. Although the MFC didn't break
> > anything, the tunables don't get changed by the values in /boot/loader.conf.
> > 
> > By applying a patch like this:
> >  SYSCTL_DECL(_vfs_nfsd);
> >  int	nfsrv_statehashsize = NFSSTATEHASHSIZE;
> > +TUNABLE_INT("vfs.nfsd.statehashsize", &nfsrv_statehashsize);
> >  SYSCTL_INT(_vfs_nfsd, OID_AUTO, statehashsize, CTLFLAG_RDTUN,
> >      &nfsrv_statehashsize, 0,
> >      "Size of state hash table set via loader.conf");
> > 
> > they get set ok.
> > 
> > So, is this correct or have I done something stupid?
> 
> I believe that is correct. hans changed how they are declared with r267961
> and now you do not need TUNABLE_INT() on -head.
> > 
> > And, if it correct, do I commit a patch like the above directly
> > to stable/10. (It seems that TUNABLE_INT() is discouraged for -head.)
> 
> That's the correct way, afaik.
> 
> Cheers,
> Hiren

Is there a reason the sysctl tunable flag changes can't be MFC'd?
Leaving changes that widespread un-mfc'd just makes for lots of merge
conflicts as time goes on (and can also lead to merged code behaving
differently than expected).

-- Ian