Date: Wed, 2 May 2007 13:53:36 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Christoph Hellwig <hch@infradead.org>, Andi Kleen <andi@firstfloor.org>,
       linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, wfg@ustc.edu
Subject: Re: 2.6.22 -mm merge plans
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On Wed, 2 May 2007 16:36:27 -0400
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> * Christoph Hellwig (hch@infradead.org) wrote:
> > On Wed, May 02, 2007 at 09:47:07AM -0700, Andrew Morton wrote:
> > > > That doesn't constitute using it.
> > > 
> > > Andi, there was a huge amount of discussion about all this in September last
> > > year (subjects: *markers* and *LTTng*). The outcome of all that was, I
> > > believe, that the kernel should have a static marker infrastructure.
> > 
> > Only when it's actually useable.  A prerequisite for merging it is
> > having an actual trace transport infrastructure aswell as a few actually
> > useful tracing modules in the kernel tree.
> > 
> > Let this count as a vote to merge the markers once we have the infrastructure
> > above ready, it'll be very useful then.
> 
> Hi Christoph,
> 
> The idea is the following : either we integrate the infrastructure for
> instrumentation / data serialization / buffer management / extraction of
> data to user space in multiple different steps, which makes code review
> easier for you guys, or we bring the main pieces of the LTTng project
> altogether with the Linux Kernel Markers, which would result in a bigger
> change.
> 
> Based on the premise that discussing about logically distinct pieces of
> infrastructure is easier and can be done more thoroughly when done
> separately, we decided to submit the markers first, with the other
> pieces planned in a near future.
> 
> I agree that it would be very useful to have the full tracing stack
> available in the Linux kernel, but we inevitably face the argument :
> "this change is too big" if we submit all LTTng modules at once or
> the argument : "we want the whole tracing stack, not just part of it"
> if we don't.
> 
> This is why we chose to push the tracing infrastructure chunk by chunk :
> to make code review and criticism more efficient.
> 

I didn't know that this was the plan.

The problem I have with this is that once we've merged one part, we're
committed to merging the other parts even though we haven't seen them yet.

What happens if there's a revolt over the next set of patches?  Do we
remove the core markers patches again?  We end up in a cant-go-forward,
cant-go-backward situation.

I thought the existing code was useful as-is for several projects, without
requiring additional patching to core kernel.  If such additional patching
_is_ needed to make the markers code useful then I agree that we should
continue to buffer the markers code in -mm until the
use-markers-for-something patches have been eyeballed.

In which case we have:

atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-alpha.patch
atomich-complete-atomic_long-operations-in-asm-generic.patch
atomich-i386-type-safety-fix.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-ia64.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-mips.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-parisc.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-powerpc.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-sparc64.patch
atomich-add-atomic64-cmpxchg-xchg-and-add_unless-to-x86_64.patch
atomich-atomic_add_unless-as-inline-remove-systemh-atomich-circular-dependency.patch
local_t-architecture-independant-extension.patch
local_t-alpha-extension.patch
local_t-i386-extension.patch
local_t-ia64-extension.patch
local_t-mips-extension.patch
local_t-parisc-cleanup.patch
local_t-powerpc-extension.patch
local_t-sparc64-cleanup.patch
local_t-x86_64-extension.patch

  For 2.6.22

linux-kernel-markers-kconfig-menus.patch
linux-kernel-markers-architecture-independant-code.patch
linux-kernel-markers-powerpc-optimization.patch
linux-kernel-markers-i386-optimization.patch
markers-add-instrumentation-markers-menus-to-avr32.patch
linux-kernel-markers-non-optimized-architectures.patch
markers-alpha-and-avr32-supportadd-alpha-markerh-add-arm26-markerh.patch
linux-kernel-markers-documentation.patch
#
markers-define-the-linker-macro-extra_rwdata.patch
markers-use-extra_rwdata-in-architectures.patch
#
some-grammatical-fixups-and-additions-to-atomich-kernel-doc.patch
no-longer-include-asm-kdebugh.patch

  Hold.

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