LOCK_PROFILING in -stable

[John Baldwin]

On Wednesday 24 October 2007 03:44:52 pm Kris Kennaway wrote:
> John Baldwin wrote:
> > On Sunday 21 October 2007 04:56:30 am Kris Kennaway wrote:
> >> Alfred Perlstein wrote:
> >>> * Robert Watson <rwatson at FreeBSD.org> [071020 10:21] wrote:
> >>>> On Sat, 20 Oct 2007, Kris Kennaway wrote:
> >>>>
> >>>>> Alfred Perlstein wrote:
> >>>>>> Hey guys, I have LOCK_PROFILING done for a product based on 
FreeBSD-6, 
> >>>>>> this means I can relatively easily backport LOCK_PROFILING from 
> > FreeBSD-7 
> >>>>>> to FreeBSD-6.
> >>>>>>
> >>>>>> Do we want this?
> >>>>>>
> >>>>>> I'd like to do it if people want it.
> >>>>> I think it should be done, performance is a lot better than the old 
6.x 
> >>>>> version and it also adds another very useful performance metric (time 
> >>>>> spent waiting for the lock).  The only concern is that it doesn't 
break 
> >>>>> ABI support when not compiled in, but I'm pretty sure you've already 
> > told 
> >>>>> me this is OK. Thanks for looking at this.
> >>>> This is my feeling also -- I would consider ABI breakage a show stopper 
> > for 
> >>>> 6.x, but feel otherwise that the new code is much more mature and 
capable 
> >>>> and would be quite beneficial to people building appliances and related 
> >>>> products on 6.x. You might check with Attilio about whether there are 
any 
> >>>> remaining outstanding issues that need to be resolved first, and make 
> > sure 
> >>>> to send a heads up out on stable@ and put a note in UPDATING that the 
> >>>> option and details have changed.
> >>> I still get confused as to the meaning of this...
> >>>
> >>> It only breaks ABI when it's enabled.
> >>>
> >>> I think that is OK, right?
> >>>
> >> Yes, that is fine.  Other existing debugging options also break ABI when 
> >> enabled, so it's OK.
> > 
> > Well, MUTEX_PROFILING does and LOCK_PROFILING is the same thing.  This 
option 
> > is a known "special case" that breaks the ABI and people using it should 
> > already be aware of that.  Other debugging options (INVARIANTS, WITNESS, 
> > etc.) do not affect the ABI.
> > 
> 
> DEBUG_VFS_LOCKS and/or DEBUG_LOCKS also break the ABI.

True, but those are the exception rather than the rule.

-- 
John Baldwin