LOCK_PROFILING in -stable
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.
Kris
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