Re: [PATCH] arm64: defconfig: Disable DEBUG_INFO

From: Mark Brown <broonie@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	Guillaume Tucker <guillaume.tucker@collabora.com>,
	Kevin Hilman <khilman@baylibre.com>
Subject: Re: [PATCH] arm64: defconfig: Disable DEBUG_INFO
Date: Thu, 4 Mar 2021 15:18:53 +0000	[thread overview]
Message-ID: <20210304151853.GC4731@sirena.org.uk> (raw)
In-Reply-To: <20210304144833.GB21410@willie-the-truck>

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On Thu, Mar 04, 2021 at 02:48:34PM +0000, Will Deacon wrote:
> On Thu, Mar 04, 2021 at 02:36:47PM +0000, Mark Brown wrote:

> > they allocate to jobs (that's certainly what KernelCI does).  Testing
> > modified versions of configurations isn't great as half the point of
> > using the standard configurations is that everyone's working to the same
> > thing and should in theory be seeing the same stuff, it's easier to name
> > a standard config than name a standard config and a list of tweaks
> > applied to it.

> I'd be fine if arm64 build reports came back as "defconfig+DEBUG_INFO=n"
> and the CI just ran ./scripts/config -d DEBUG_INFO as part of its build
> step. For runtime testing, however, having the full vmlinux available is
> really helpful if we need to debug.

Note that one of the things people are working on at the minute is
trying to aggregate results from different systems together.  Like I say
it's more a case of just allocating more space to these builds rather
than some insurmountable thing that can't be handled.

> > This is about picking a sensible default, there's always going to be
> > cases where someone wants the other value (otherwise it wouldn't be a
> > config option).  The contention is that there's a lot more builds being
> > slowed down by the extra I/O and disk space being burned than benefit to
> > people who end up with the debug info turned on and actively use it but
> > these aren't direct tradeoffs so you can't categorically say something
> > one way or the other.  At the minute defconfig actually results in a
> > bigger build tree than an allmodconfig for me (6.8G vs 5.2G) which
> > doesn't seem like what I'd expect.

> I suppose I'm of the opinion that debug info is a waste of time until you
> need it, and then it's suddenly invaluable. So I'd prefer it to be there by
> default, as I don't think the extra I/O or disk space is a concern outside
> of CI. But it would be good to hear what others have to say.

FWIW with laptops the I/O cost tends to make a difference to the
edit/compile/run time for me, disks are slow and RAM not plentiful.
Right now I'm sitting at a rather high speced desktop so the build trees
I got the storage numbers from were all in RAM backed tmpfs and it makes
very little odds.

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