linux-kernel - Re: [PATCH] riscv: defconfig: k210: Disable CONFIG

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Message-ID: <CAMuHMdXEzo4EOw_=MgskNXPrbkP4Ui+dHKZ5iyJ04h453BUAhQ@mail.gmail.com>
Date:   Wed, 25 Nov 2020 10:26:02 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Damien Le Moal <Damien.LeMoal@....com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] riscv: defconfig: k210: Disable CONFIG_VT

Hi Damien,

On Wed, Nov 25, 2020 at 10:02 AM Damien Le Moal <Damien.LeMoal@....com> wrote:
> On 2020/11/25 17:51, Geert Uytterhoeven wrote:
> > On Wed, Nov 25, 2020 at 7:14 AM Damien Le Moal <Damien.LeMoal@....com> wrote:
> >> On 2020/11/25 3:57, Geert Uytterhoeven wrote:
> >>> There is no need to enable Virtual Terminal support in the Canaan
> >>> Kendryte K210 defconfigs, as no terminal devices are supported and
> >>> enabled.  Hence disable CONFIG_VT, and remove the no longer needed
> >>> override for CONFIG_VGA_CONSOLE.
> >>>
> >>> This reduces kernel size by ca. 65 KiB.
> >>
> >> Indeed, nice saving. Just tested, and all is good.
> >
> > I used my old script[1] to check the impact of disabling config options.

> > I haven't done enough riscv kernel development yet to assess if I need
> > CONFIG_FRAME_POINTER or not.
>
> Disabling it significantly reduced code size for me. Since the series is more
> stable now, it is not really needed, so I disabled it in the defconfig.
>
> I was just fiddling with CONFIG_UNIX98_PTYS. Disabling it is OK with the simple
> busybox userspace (no telnet/xterm like app running). But it saves only about
> 1KB with my toolchain (gcc 9.3). So I left that one enabled. I am surprised that
> you see 16K size impact... How big is your image ?
>
> For me, it is 1.768 MB right now for the sdcard defconfig, with CONFIG_VT
> disabled and ext2 enabled.

It might depend on how you measure.  "size" says 15 KiB impact for UNIX98
ptys, while bloat-o-meter reported less than 7 (my script uses "size").

I'm at 1.88 MiB, with ext4 and without frame pointers.
I also got rid of the EFI partition support, and a few I/O schedulers:

+CONFIG_PARTITION_ADVANCED=y
+# CONFIG_EFI_PARTITION is not set
+# CONFIG_MQ_IOSCHED_DEADLINE is not set
+# CONFIG_MQ_IOSCHED_KYBER is not set

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds