Re: setting tunables in stable/10 vs head?

On 06/10/15 at 10:07P, Ian Lepore wrote:
> 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).

Added Hans to answer the question.

Cheers,
Hiren