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SubjectRe: [PATCH] x86: numa: setup_node_data(): drop dead code and rename function
On Wed, 2 Jul 2014, Luiz Capitulino wrote:

> > With this patch, the dmesg changes break one of my scripts that we use to
> > determine the start and end address of a node (doubly bad because there's
> > no sysfs interface to determine this otherwise and we have to do this at
> > boot to acquire the system topology).
> >
> > Specifically, the removal of the
> >
> > "Initmem setup node X [mem 0xstart-0xend]"
> >
> > lines that are replaced when each node is onlined to
> >
> > "Node 0 memory range 0xstart-0xend"
> >
> > And if I just noticed this breakage when booting the latest -mm kernel,
> > I'm assuming I'm not the only person who is going to run into it. Is it
> > possible to not change the dmesg output?
>
> Sure. I can add back the original text. The only detail is that with this
> patch that line is now printed a little bit later during boot and the
> NODA_DATA lines also changed. Are you OK with that?
>

Yes, please. I think it should be incremental on your patch since it's
already in -mm with " fix" appended so the title of the patch would be
"x86: numa: setup_node_data(): drop dead code and rename function fix" and
then Andrew can fold it into the original when sending it to the x86
maintainers.

> What's the guidelines on changing what's printed in dmesg?
>

That's the scary part, there doesn't seem to be any. It's especially
crucial for things that only get printed once and aren't available
anywhere else at runtime; there was talk of adding a sysfs interface that
defines the start and end addresses of nodes but it's complicated because
nodes can overlap each other. If that had been available years ago then I
don't think anybody would raise their hand about this issue.

These lines went under a smaller change a few years ago for
s/Bootmem/Initmem/. I don't even have to look at the git history to know
that because it broke our scripts back then as well. You just happened to
touch lines that I really care about and breaks my topology information :)
I wouldn't complain if it was just my userspace, but I have no doubt
others have parsed their dmesg in a similar way because people have
provided me with data that they retrieved by scraping the kernel log.


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