Kris Kennaway kris at FreeBSD.org
Wed Oct 24 12:44:52 PDT 2007

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.


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