Date: Wed, 24 Oct 2007 16:08:08 -0400 From: John Baldwin <jhb@freebsd.org> To: Kris Kennaway <kris@freebsd.org> Cc: stable@freebsd.org, Alfred Perlstein <alfred@freebsd.org>, Robert Watson <rwatson@freebsd.org> Subject: Re: LOCK_PROFILING in -stable Message-ID: <200710241608.09298.jhb@freebsd.org> In-Reply-To: <471FA0B4.1000904@FreeBSD.org> References: <20071019232846.GQ31826@elvis.mu.org> <200710241310.22969.jhb@freebsd.org> <471FA0B4.1000904@FreeBSD.org>
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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@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
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