Re: [PATCH] arm64: defconfig: Disable DEBUG_INFO

From: Kevin Hilman <khilman@baylibre.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Guillaume Tucker <guillaume.tucker@collabora.com>
Subject: Re: [PATCH] arm64: defconfig: Disable DEBUG_INFO
Date: Thu, 04 Mar 2021 09:24:15 -0800	[thread overview]
Message-ID: <7hzgzi3k8w.fsf@baylibre.com> (raw)
In-Reply-To: <20210304162231.GA29547@arm.com>

Catalin Marinas <catalin.marinas@arm.com> writes:

> On Thu, Mar 04, 2021 at 03:18:53PM +0000, Mark Brown wrote:
>> 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.
>
> I found DEBUG_INFO pretty useful as well and always hated it in the past
> when I had to recompile a kernel just to rerun the tests and identify
> the source/line of an address (I guess that's why we ended up with this
> in defconfig).
>
>> > > 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.
>
> How about enabling DEBUG_INFO_REDUCED as a middle ground? For me the
> build tree goes from 5.9GB to 2.0GB. I tried faddr2line and still works
> as expected (only tried gcc, not sure whether clang honours this
> option).

Sounds great to me.

Kevin

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel