Date: Wed, 24 Oct 2007 13:10:22 -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: <200710241310.22969.jhb@freebsd.org> In-Reply-To: <471B143E.7050200@FreeBSD.org> References: <20071019232846.GQ31826@elvis.mu.org> <20071020192717.GX31826@elvis.mu.org> <471B143E.7050200@FreeBSD.org>
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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. -- John Baldwin
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