linux-kernel - Re: [PATCH] RISC-V: Add debug defconfigs

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Date:   Thu, 5 Dec 2019 22:39:59 +0530
From:   Anup Patel <anup@...infault.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Anup Patel <Anup.Patel@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Atish Patra <Atish.Patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        Christoph Hellwig <hch@....de>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RISC-V: Add debug defconfigs

On Thu, Dec 5, 2019 at 10:17 PM Daniel Thompson
<daniel.thompson@...aro.org> wrote:
>
> On Thu, Dec 05, 2019 at 10:03:34PM +0530, Anup Patel wrote:
> > On Thu, Dec 5, 2019 at 8:33 AM Paul Walmsley <paul.walmsley@...ive.com> wrote:
> > >
> > > On Thu, 5 Dec 2019, Anup Patel wrote:
> > >
> > > > Various Linux kernel DEBUG options have big performance impact
> > > > so these should not be enabled in RISC-V normal defconfigs.
> > > >
> > > > Instead we should have separate RISC-V debug defconfigs having
> > > > these DEBUG options enabled. This way Linux RISC-V can build both
> > > > non-debug and debug kernels separately.
> > >
> > > I respect your point of view, but until the RISC-V kernel port is more
> > > mature, I personally am not planning to merge this patch, for reasons
> > > discussed in the defconfig patch descriptions and the subsequent pull
> > > request threads.
> > >
> > > I'm sure we'll revisit this in the future to realign with the defconfig
> > > debug settings for more mature architecture ports - but my guess is that
> > > we'll probably avoid creating debug_defconfigs, since only S390 does that.
> >
> > We have a lot of users (Yocto and Buildroot) dependent on the Linux
> > defconfig. I understand that you need DEBUG options for SiFive internal
> > use but this does not mean all users dependent on Linux defconfig
> > should be penalized in-terms of performance.
> >
> > This is the right time to introduce debug defconfigs so that you can
> > use it for your SiFive internal use and all users dependent on normal
> > defconfigs are not penalized in-terms of performance.
> >
> > If you still don't want debug defconfigs then I recommend reverting
> > your DEBUG options patch and you can find an alternative way to
> > enable DEBUG options for SiFive internal use.
>
> None of my business (except that I watch threads with debug in the
> subject line) but why propose putting debug options into any kind
> of defconfig. If you want standardized set debug options to chase
> problems why can't they into a .config file rather than a defconfig
> file.
>
> In use it will look like:
>   make defconfig extra_debug.config
>
> That way you don't have to maintain two almost identical files that will
> inevitably drift apart.

This is a good suggestion. I will certainly try it out at my end and send
a v2 with "extra_debug.config" file.

Thanks,
Anup